MAKE SURE YOU TRY IT ON (as mentioned in Mr. Schlegel's post) Size matters and bigger isn't better.

For the last 3 years, I have been playing an ovation acoustic guitar, given as a gift 20+years ago...anyways...it was way to big for me but I couldn't buy one so I used what I had. it was very hard to adequetly accomplish the skills taught in the beginning lessons (fundementals - chords and barr chords). my philosophy was, if I can learn on a guitar I have to work harder on, I would be better later... (I heard some famous person say that...cant remember who... but I adopted that philosophy because I had too) I'm not sure if that philosophy holds true...but maybe I gained something.

Just about a month ago, I got a baby taylor (used and relatively inexpensive) for a gift and I can't believe the difference size makes. my progess and ability to reach chords and do barre chords dramatically increased.

Even now, after "passing" fundamentals level and moving on, I'm not sure how to go buy a guitar but Sweetwater (referenced earlier in a post) has a "buyers guide" and can teach you a little. and of course all the advice you can get here.

do your homework!