If you want to buy a guitar, you shouldn't just buy the first guitar that looks good to you. Go to your local Guitar Center, or music shop. Ask for help. Make the guys work. Most of them love helping someone find a guitar.
The first step is to establish your price range; it narrows down the choices. Next, ask for an recommendation of guitar types. If you are into playing rock, a dreadnought acoustic guitar made by Martin wouldn't be a good choice. Ask for a recommendation of a good brand. When you see a guitar that stands out, ask to try it out. The guys at Guitar Center will let you plug into just about any of the amps lying around. Get a feel for the guitar, and it's strong and weak points, (ie, weight, size, overall feel) Rip out some scales and power chords. Is the sound full, or tinny? Make sure you try out a lot of guitars so you can have an active comparison. OK, so now you know you have your guitar now. You know it's the one for you. Well, hold on, partner, don't break out the credit card yet. Guitar Center is a good place to buy a guitar, but its not the only one. Make sure you remember which guitar you have chosen, say thanks to the guy who helped you, and walk out. When you get back home, log on to a music instrument site like Musiciansfriend.com, to compare prices. If Guitar center had the best price, drop in later, and walk your guitar to the counter. Finally, after you buy your guitar, ask if the cashier will throw in a gig bag, or a case (if its a high-end guitar), some strings, picks, etc. Always try to get the most out of your purchase. You might want to invest in a warranty if you plan to play your guitar often. Finally, have the door man check your receipt and you've got your self a brand new guitar, and you might have saved some money too! Good luck and happy jamming!