This is in reply to Bob's question about recording keyboards. Sorry to get off the initial topic, but it's really related.
A guitar, electric or acoustic, is fundamentally a monophonic instrument and should normally be treated as such. For that matter, so are conventional synthesizers. Romplers, OTOH, usually feature stereophonic samples or effects that would seem to warrant stereophonic recording. There are, however, benefits to recording even those instruments in mono.
Romplers and software sample players are designed to sound good in the music store: full, fat and wide and all-enveloping. Trouble is, that's exactly what you
don't want in a complex music production. Rather, you want each voice in the mix to have its own well-defined place in both the panorama and in the frequency spectrum. Mono tracks give you more mix options, and actually result in a better sense of stereo width in the final product.
Don't worry about losing anything by recording your Motif, Fantom or Triton in mono. Most of their samples aren't true stereo anyhow, but are just effected in ways to give the illusion that they are. Most patches sound just fine either collapsed to mono or just recording one side.
(One exception comes to mind: Leslies. That's a true stereo source that needs to be recorded in stereo for best effect. But even then, stereo may not be necessary. Deep Purple's sound was heavily dependent on the Hammond sound, but it was not, AFAIK, ever recorded in stereo. It's usually mono but given width with effects and pan movement.)
Back to topic: the vast majority of guitar tracks heard in commercial recordings are monophonic, as are most acoustic guitar tracks. Of course, they don't
sound mono, but that's because you're either hearing more than one guitar, or a stereo effect - not because the part was originally recorded in stereo.
What was the question again? Oh, yeh. How to record in stereo. The flippant answer is "don't".
But if you really want to record a stereo guitar track you must start with an actual stereo source. Two mics on the same speaker cabinet do not make a stereo source. Two amplifiers with different effects and tone settings positioned on opposite sides of the room, that's a real stereo source. One close mic and another distant room mic could be treated as a stereo source. Guitar through a Leslie, that'd be stereo. And that's about it.