I have taped over 100 shows in my time, of all kinds of bands, and this is a simple breakdown that might get you making your best tapes as soon as possible, since there is a great deal of learning about what to do.
Equipment
These days you should pretty much make sure you are dealing with the digital realm, this means preferably a DAT, secondarily a minidisk. Why I list a DAT as preferable is there is less room for error, and many people get suckered into buying a lower level minidisk that creates big problems.
Advantages of DAT, you never have to change media for a U2 show, You can probably do this tour on a 120min DAT or 180min, in 44.1 or 48 and not have problems. With Minidisk your gonna have to do the dreaded "tape flip" once during the gig, a screwed up tape flip means your the sucker with the incomplete gig while the other 20 guys that taped the show probably will not have that problem. (the solution is NOT to run in mono for 150 minutes, as dumb as this sounds, some people I know did this) .Therefore from the start, you are the one with the "bad version". It also has come to my attention that many minidisk players do not have Digital Outs for some crazy reason, i.e. you go to all the trouble to tape in digital then your taking an analog cord out. DATs do not have this problem at all, they all have digital outs and in these days. And a final problem that does occur on some minidisk players is they do not have the ability to adjust recording levels once recording has started, this is a huge problem, as your tape may get overloaded or be to distant and there is nothing you can do about it.
So there are some minidisk recorders that avoid these problems, but be aware of the above so you can get the proper kind of machine (search the net, there are several sources such as datheads that will give you more than enough data on this)
Microphones all vary, some of the best recordings of u2 ever made according to you the fans, are ones done with $500-$700 sets of mics such as Sonic Studios, Core and OKMII rock versions. If you do have the ability to spend lots of money you can buy expensive mics such as schoeps, nakamichi, neuman, etc.Bear in mind though these are more for taper friendly bands where you can be seen using them (there big mics many time). Further disadvantages of these mics is they require heavy cabling, and more chances for things to go wrong. You can use a SBM1 as well to digitally map your tape before it goes into your DAT,(your dat does this as well, but some argue not as well) and my view on that piece is its a marginal piece of equipment, i have taped with it and without it, and I have better tapes sometimes without it than with it. It is another thing that can go wrong in the process. Its another set of cables, batteries, setting levels etc, and the more variables that can go wrong, and you could end up with a faulty master.
Showtime
Now your there, with your eqipment at the show, you have approached the most critical moment of the entire process. I believe 90% of what makes the sound of a tape is positioning. The other 9% comes down to mics and digital device and last 1% might be peripheral crap (sbm, other gizmos). The first item to do, and hopefully you did it when selecting your tickets, is to select the correct spot. The correct spot means the correct spot to you, depending on what type of sound you like, since after all it is your master.With the graphics below we illustrate some different spots and how they will effect your tape.

The two most common spots are A and B, but they will give you different sounds for sure
Spot A
Spot A is probably the most common taping spot, the general operating principle to this spot is you have minimized your distance to the sound source. Therefore, you will have much higher relative levels of music to audience. This allows you again on a relative level to set your levels low and keep the audience noize out. Whenever you see a tape mislabeled as soundboard its usually from this spot because the audience noize is very limited. Another advantage of being on the sides right in front of the speakers is the crowd is less dense than in the center where the band is. You will have sort of a weak sight line to the stage compared to the center, but you will have more space to operate. You do not want to be on the barrier, more like 10 yards back. If your to close you loose some of the high end that will fly out of the speakers high above, and you might blow out your recording with Bass. There can be one disadvantage to this spot, and one that sometimes send people directly to spot B. This is heavy panning of instruments, while this is not usually a problem with U2, some bands will use hard pans on each side so if your on edges side you get lots of Edge and Bono and less Larry and Adam.. Also if a band is using many stereo effects, you will not pick them up as well on the sides...basically your deciding little audience noize and thumping instruments vs stereo effects.
Prominent gig from Spot A include
Anhaheim 92, Las Vegas 92, Meadowlands 8-13-92, Berlin 93,
Stuttgart 93, Rotterdam 93, Vienna 92, Wembley Nights series, Dublin 83
Spot B
This spot is also a preffered location. It is the spot you will see frequently mentioned on DAT heads, and that many of the taping friendly people use. Here you literally look at the stage and scaffolding and find the dead-center perfect spot equidistant from the speakers. If there are stereo effects or heavy panning you catch everything dead perfect here. Due to the angle of speakers though, you must stand somewhere usually halfway between the soundboard and the stage. What you can do is find the dead center and during opening act walk as far forward as you can before you notice a significant drop in high end achieved by you basically getting in back of the speaker angle.. Usually you can see this spot, especially in an arena show by basically drawing a imaginary line in your head from the edge of the two innermost speakers (tilted towards center) and seeing where it intersects. Downsides of this spot is that your relative audience to speaker noise is much higher here, and epecially with u2 cause you have to do with geeks around the mini stage going nuts...The accomplised taper will bring his buddies along with him to give him a body or two buffer from screamers and other assorted drunks.
Prominent gigs from Spot B include
Houston 85, San Francisco 4-24 and 4-25-87, Oakland 4-18-92,
Spot C
Spot C is the same as spot B except too far back, here you incur to much audience noise. Outdoors you have to deal with problems with wind back here distorting the signal, and indoors this far back gives you more exposure to echoes and booms from the arena which can be painful with sonic studio mics. Usually people dont choose to tape from here, rather they are stuck with it.
Prominent gigs from Spot C include
Boston 9-18-87, Los Angeles 87 indoor, virtually all of them, Dublin
6-27-87
Spot D
Spot D is the location that is sort of far off on the side, in an arena this means maybe 30-40 yards back from stage, outdoors maybe 50-75 yards. Again here usually you are seated, so you have more operating space. You will be subject to echoes in an indoor show and distance on outdoor shows. Usually people who select this spot do not do it out of choice, either they could not get a better ticket or they choose not to stand. Its hard to do a great tape from this location
Prominent gigs from Spot D include
Budapest, Naples 93, Cologne 87,
Spot F
Only tape from here if you really want to, indoors your looking at mountains of echo, low levels, and people talking. Outdoors your just to far way from the sound source.
Prominent Gigs from Spot F include
none
Spot G
This can be a surprise spot, sometimes on the side of the stage you can get very close to the wraparound pa much like spot A. Better yet sometimes it is sparsely inhabited and you can get in the first row that literally hangs over the stage, i.e. nothing between you and the speakers. Since you are higher sometimes you can almost reach out and touch the PA. There have been some great tapes done here.
Prominent Gigs from Section G include
Gent 92, Rotterdam 1-10-90, Kiel 92, Tacoma 92
Ok, Im in my spot, what to do now
Showtime approaches, be aware of what the intro song will be as it will probably be known after the first gig in Miami, then halfway through that fire up the AT and get your eqipment running. Do it slowly to avoid a mistrack and make sure you are hitting all the buttons in proper sequence.
Mount your mics in a hat, THIS IS A HUGE POINT. This past year I went to Europe to record another band with some friends who have recorded virtually 10 years mounting the mics on a jacket. They realized the difference in sound quality after a couple of shows where we ran identical equipment, stood side by side, set the same levels and my tape came out more cleaner. if you doubt this, next time your packed in an arena, lean down your head to where your jacket pockets would be, and listen to how much high end you loose. Hats get the mics up above the heads and give you an unimpeded line to the speakers, greatly eliminate the sounds of people moving in front of you. Baseball hats are not common in europe so you do look a bit unique with them, but simply cut a tiny hole in the front of one for each mic and have the mic barely protrude from the hole. When the lights are down , nobody notices the wires (buy a black hat, that's obvious).
Once the dat is running and the mics are going, just enjoy the show. Remember not to look at your levels 100x during the gig, if you screwed it up you don't want to know it anyway....Just check the first couple of songs, or when a loud song hits. Don't push the levels to the top, as you don't need to. More people get caught looking at there stupid dat levels than by any other means, and its not even close....Put the hold button on as well, and tape down your levels once there where you want them (i always use the dat labeling sticky that comes in the dat cassette box)
That's it, I am sure professionals could pick this apart, but this is
intended to get the common man up to speed quickly. If it means no more
jacket recorded tapes we are already ahead of the game. Positioning is
the key, and the other things fall into place.
Elevation Tour Specific Info (new 4-21-01)
Ok so I am just back from 6 gigs now and I have some ideas on the audience taping. First of all I must say it will be a bit tougher to do this tour due to the fact that the show is so natural, heartfelt, and great that there is 10x the audience participation than previous couple of tours. Bottom line is it's deafning in the arena.
The actual PA is crystal clean, and most resembles the sound from Spring 87. It is much cleaner than the zoo tv indoor setup which actually usually sounded very muddy the first few songs. It is not chunky and dry sounding like the fall 87 U2 pa indoor setup. It seems since all the shows are indoors it tailored for that purpose.
As for the best spots, there spots B and G listed above in the guide. Due to the fact there is no PA stack on side stage, only hanging high above , there is no spot A this tour..Heck you cant even get to spot A this time, it doesnt exist. There are no speakers at all on the stage besides monitor wedges for the band.
I have heard completely different opinions now on taping in the heart. A couple people who i know tried to do it in Miami said it was a disaster as far as crowd noize, they said the pa was good there, but you keep having people come by you, and when there on the catwalk and your trying to take dead aim at center stage, you have people looking directly in the whites of your eyes watching bono at the tip and signing literelly right into your mics. Some people didnt have this problem , some did, it seemed in a much more mellow enviorment being charlotte it was not as boisterous in there, and your chances were better. So it is a tape at your own risk situation, it is the highest risk reward, it could be totally great, it could completely blow up in your face in that it might just be some chick singing into your mics when bono is out at the tip (which is at least 50% of the show). I admit I dont like high risk reward, I want to make sure its not something terrible, and someone signing out of pitch and out of tune into my mics is terrible, likewise a sit and spin swivel where it sounds like a tornado if i have to turn around 100 times in all directions to play like the crowd and follow bono.

About 15 feet back from the tip of the heart is probably the best spot on floor, (see white dot in picture above) your at the proper angle to catch the stereo reflection from each side. After seeing 6 shows this is my favorite spot, many people including people I respect highly for there opinion on where sound is good all choose this space, there is no mystery as to why there is 15 tapers all standing dead center half way between the desk and the tip. Also your far enough back to not catch all the screamers so your tape comes out extremely smooth. I have walked directly out of the heart into this spot during the same song and noticed much better levels at the tip than inside the heart. Inside the heart you catch a great deal of dry amp sound off Edge and Adam's amps and Larrys drum kit, but the vocals can get lost because there only coming out of the PA that is shooting sound out above your head. That little mini stack pointed at the point does not provide the punch the main PA does
There are some areas where you can get close up to the pa on the outside
of the catwalk around the entrances to the heart. Only problem here it
is a narrow little band and you may have security issues as well as issues
of screamers evey time Bono walks by that narrow strip.
About the seats, basically using the map below I can describe areas that will work better than others, this map is directly from national car arena, but its similar to most venues

Prime seated locations for sound are
120,121,122 and 131,132,133 rows 10-25 (close as you can get
to the main stack facing outwards
Starting to get too far away for that a1 sound
118,119 and 134, 101 ( I taped from 118, relative
audience to pa levels start to drop here)
319-334 (ok from first couple rows of these areas)
The unique spot G locations are
124, 125, 128,129 (you can catch the back pa which seemed to have relative
low audience to pa levels)
Trouble
102-117 (you are starting to get to far away to get clean up front
sound, and if you got screamers around you they could overpower the tape)..if
your using OKM IIr mics you gotta really move the level dial up a bit back
here just to get past midpoint.
Death
301-318 (to far away , will just be very distant sounding, and if screamers
are around you, they will totally overpower you)
any 400 seat
Hopefully this helps some of you out, if your new to this and your freaking because its apparent that your sitting to far away from the stage, as crazy as it sounds sometimes people behind the stage will trade seats with you so there not looking at the back of U2's heads all night (with the exception of a couple songs)..There is no question if you dont want to tape on the floor but you have a GA ticket, you could easily find someone to trade that ticket with (but do it before the gig, cause you cant swop wristbands).
bottom line, Screamers suck.