When you go to choose acoustic guitar the two most important things to look for are: how it sounds and how easily it plays.
How does it sound? Using a pick, pluck an open string (pluck it without holding it down). How long does it ring? A good guitar will ring for quite a while. You can't play a note or chord that is supposed to ring for six seconds if the guitar only rings (sustain) for two seconds!
Now pluck the bass strings,(those are the fat ones). Better guitars have deep, warm sounding bass tones, not thin or tinny sounding. Next, one at a time, pluck the treble strings. Do they sound as loud, or almost as loud as the bass strings? If they do, the guitar has a "balanced tone". You should listen for a warm rich tone, with good volume and sustain.
Next, listen for buzzing. Buzzing is caused by a string vibrating or rattling against a fret.
The difference in tone between a top quality acoustic guitar and a low quality guitar are tremendous. A poor quality guitar sounds dead and tinny, but a top quality acoustic sounds warm, and rich, with every single note sounding beautiful. As a beginner you should aim somewhere in between, that way, as you learn, your playing will sound more like music than just sound.
If you can't play yet,and you're in a music store, get the salesperson to play for you. Judge the sound independently of other features. Shiny, flashy, cool looking stuff has nothing to do with the sound, or playability of the guitar.
Things That Affect The Guitar's Tone And Price
I built an acoustic guitar about eight years ago,(you can see a picture of it in the guitar anatomy section: parts of an acoustic guitar) and the materials alone cost me $480.00 back then. The material that an acoustic guitar is built with are one of the the biggest factors to the cost of the guitar, and, the quality of the sound. I could have spent much more for the wood. For example, if I would have used Brazilian Rosewood for the backs and sides it would have cost me an extra $1000.00! I used a high quality mahogany, because, I wanted the warm, dark tone that mahogany is known for. The top is made of Alaskan Sitka Spruce, grown far north, where the trees start to disappear. It took 265 years to grow the tree thick enough for the wood on the top, (and probably twice as long just to grow the tree). These trees are disappearing and the wood is going up in price quickly! This is only part of the reason that there is such a difference in the prices of acoustic guitars. Construction methods, quality of the tuners and other attachments, and time and cost of materials used in ornamentation are the other factors.
Acoustic guitars are not only made of wood. Some of the garbage guitars are actually made of Masonite! Masonite is made with saw dust and glue compressed under pressure, and has virtually no sound transmission ability. That is what a lot of the auction site guitars that I warned you about earlier are made of.
Other guitars are completely made of a graphite and resin composite. They produce a very clear bright tone, and they never warp. They are expensive.
There are also guitars that are made of wood (usually used for the top), and composite for the back. These guitars are popular and usually have a nice sound.
Most acoustic guitars are made of laminated wood (plywood), or plywood for the backs and sides and solid wood for the sound board (top). Plywood does not transmit the vibrations needed to produce sound very well because the glue used to make it doesn't transmit sound at all, and there is usually a layer of cheap wood in the center, which goes cross ways to the grain of the outer layers further reducing the natural vibration of solid wood.
Solid wood tops are usually much better sounding than plywood tops without adding huge dollars to the price, so, if you can afford it, buy one with a solid wood top.
Watch out! Advertising can be misleading, so, I am going to help you decode its language. "Solid" means it is made from real wood, not plywood. For example; if the top is called a "spruce top" or a "cedar top", it is probably made out of plywood, not "solid" wood. The same thing goes for the back and sides. Acoustic guitars made with solid wood, or solid wood tops usually improve tonally with age. Cedar sounds better right off the bat, but, it doesn't improve much with age. Cedar is also very soft and gets nicks and dings quite easily.
Once you are satisfied with the sound, it's time to try the guitar for playability.