What You NeedAcoustic:You can record acoustic two ways. You can use a mic to mic the guitar and then run it into your computer through the line out. To do this you will need a mic. and a 1/4 to 1/8 piece which you can pick up at Radio Shack and a program. I suggest Cool Edit Pro which I find easiest for me but their are tons of others. Or if you have an electric acoustic just plug the acoustic in through the line out like before.
Electric:Their are many ways you could record an electric guitar. You could go from your amp into pedals to a mixer. Straight from your pedal to the computer.Mic the amp. It's really your choice on how you like the sound and what you find gets the best sound.
Basic Stuff To Record-A Mic (Shure SM48) 99$ Good quality to start messing around with
-A 1/4 to 1/8 Piece 2-3$
-Your Guitar
Once you get more into it their are plenty of our options.Digital which I havent ever used but throwing a mixer into the picture as well as higher quality pedals and mics will help. As well as a mic preamp.
THANKS TO HYLERWell, usually I would get technical here, start talking about frequencies, what to run, how to interface with your computer to get the best sound, etc.
But here instead of explaining why, I will just give the bare minimum to achieve a record quality tone, you can research them on your own if you like.
24/96 Interface
Mic For Acoustic (never record your acoustic using a pickup even if it's built in, preferebly a sensitive mic with a large interval of frequency range. I use an MXL Condensor)
DI For Electric along with a Mic Modeling program, or run a raw direct signal into your PC and use a VST such as Native Instruments Guitar Rig or Amplitube.
That's not asking too much. And please do not record using your amp and a mic. I'm getting so sick of hearing those failed tones. Most people cannot properly do this. They may even have a good amp, as well as a sufficient mic, but they never take room size, mic placement, post mic preamp, or VST adjustments into consideration when they do it, and they always end up sounding horrible.