I've recorded a fair bit of speech in my time, including poetry for BBC radio.
Personally (and I mean personally), I'd get them all miked fairly closely. Not right on the mic as in voiceover, but close enough so you don't hear the room. Maybe a foot or more. Aim for it to sound as if they are in the room with you.
The best formation is to have them all sitting round a table, so they can see each other. You shouldn't isolate them too much - they will often like eye-contact with each other.
Follow the script closely and ride the faders as you record. Don't mute the unused - instead dip the unused mics to about -10dB, so you can fade the next one up quicker, rather than coming all the way up from mute. You can get away with coming up from -10dB on an opening word, but in coming up from mute you'd hear the fade. If each reader has a whole poem each, then you'd probably not need to ride the faders and can get away with kiling each channel until it's needed.
Use some large diaphragm condensors. I tend to favour AKG C414s as these are relatively flat. Avoid mics like Neumann TLM 103s as these add a presence peak and will sound unnatural.
As you're dealing with poetry, you'll probably want this as natural as possible, so avoid compression. Seriously - maybe a little compression to catch any high peaks, but don't allow the voices to get too processed. Ditto EQ - use sparingly.
Make sure your performers don't drink coffee before the recording as this dries out the mouth and will add clicks and clacks. Encourage them to take plenty of water in with them. Listen out for script rustle - even the most experienced actor/VO is guilty of this one. Yes, they will argue that they didn't rustle, but you're in charge so make them do it again... Make sure the readers read the script with their eyes, not their head. By that I mean that a reader can have the habit of bending his head downwards as he reads, and you can hear the sound change as he gets further down the page - keep that head still! Look out for loudly ticking watches, jangley jewelry (my personal nightmare is having to record Mr. T). And say 'no' to laptops - sound obvious, but I've made presenters print out their script during studio time because they thought their 'quiet' laptop with their script on wouldn't pick up on the mic...
Good luck,
A47.
it might be a good idea to know what kind of mood the poets want to set though, and then you can record it so it best reflects that mood
