there is a good article on this subject in the new issue of Recording magazine. Basically because of the way the guitar resonates, you want a good stereo image from like a pair of small diaphram condensors, in a decent sounding room. Because the source is not very loud low self noise and noise in the room or from other equipment, or chairs for that matter, are important considerations.

Another thing that will have to be thought of is if you guitarist is working off a sheet music stand. I don't even want to think about having to deal with it and it's reflections, I'm sorry I brought it up-- but if the guy is reading off a stand it will complicate things further.

Cool, I just bought the mag and read the article.

Couple things I didnt get in the article.

"...with spaced omnis: the monophonic compatability is potentially poor, as the two spaced microphones, when combined in a single channels can produce a comb filter effect..."

Is this saying that you should record each mic to a different track? Is it talking about phase issues?

Also, the article does not say anything about Pre amps.

My choices are Benchmark Media MP300 or Millennia M-2b. My available mics are Neumann 183 or 184 stereo pairs.

That is exactly what he is talking about: phase issues, comb filtering, mono compatibility I guess are different aspects of essentially the same problem.

To mehe article gives a decided preference to M-S technique, but it is quite clear that for results they are talking about a good sounding room is number one (or two or three, depending on how you rank the guitarist and the guitar), and the equipment being up to the task.

If you have each of those pairs of mics available to you, try both and see which works best. If your room ends up not being "good enough" for omni try the 184's in like the xy or ortf. The key I'd think is to: try as many ways as you can, test how the sound in your space, and tweak the mic placement, rather than lock into one way now.

I'm sure you'll do fine. Let us know how it goes, and how you end up tackling the problem.

I have heard of people placing a mic near the neck also.

Well, I think that experimentation is key if you haven't done someting like this before. Maybe for the sake of learning, it would be a good idea to use a lot of mics to separate tracks and solocombine them after the fact.
As for the cob filter effect, if you keep them within a foot of each other they sould be okay. If your room doesn't sound great, then I would substitute your omni mics for cardioid and experiment with the best positioning.

Steve.