Hi Charles, great that you are going to try recording both at once! As timidi has explained, there are limitations which will be imposed on you come editing and mixing time doing it this way - now that's not necessarily a bad thing, but you need to be aware of it.
Firstly, you need to have a clear idea of how you want the final product to sound. If you want an up-close, stereo 'pop' sound, then you're going to be limited in the extent to which you can achieve this effect by recording vox and gtr simultaneously. Reason being that you will inevitably get a fair amount of vocal bleed in your guitar mics, so when you pan them to give the guitar a bit of a stereo spread, the vocals are going to feel unstable, like they're wandering, due to phase issues. If you want your guitar to have a bit of width, then I've found the best way is to mic up the guitar in stereo, record a DI signal too, and make sure you use bi-directional mics on the guitar and vocals in order to try and minimize vocal bleed. That way you can increase the overall guitar:vocal ratio by mixing in the DI signal, and still get a bit of width and 'true tone' by mixing in the 2 guitar mics.
Another option is to forget a stereo guitar, and just record the DI and a single mic on the guitar. Again, best to use a bi-directional mic on guitar and vocals. But do spend the necessary time placing the guitar mic to achieve a well balanced sound. The guitar has a complex and uneven frequency radiation pattern, so it can be very easy to 'spotlight' a certain section when close-micing, and be left with an unbalanced tone.
One thing you definitely should not do is to record both a DI signal and a mic on the guitar, and then hard pan them. Obviously you're going to get a whole of vocal in the guitar mic, so if you hard pan this, it's going to screw up your stereo field and make the listener feel on edge.
Another option is to use a single, well placed mic, usually in omni, and the DI signal. But to get good results here, you MUST have a good sounding room, and you MUST spend a lot of time on placing your single mic. You will also need to mix yourself as you play.
My advice would be to try all of the above, and more - you don't know bad taste until you've been there! The key is to experiment and listen. It won't do any good me saying, "put this particular mic here, this one here, and this one here" because it is truly amazing how different everyone sounds. But as I've said, a good place to start is with bi-directional mics all round, as this will help to minimize bleed. Have fun, and post some samples!
post edited by jamescollins - 2011/11/28 22:00:33