Can't rock out without a good amp, right? When buying a guitar amplifier, it's easy to get something that will over-perform or won't meet your needs. To find the amp that fits you best, there are a few things you should take into consideration.
First, when buying a guitar amplifier, don't buy something that is too large. Too large can mean physically too large for your practice space, or too much wattage. Consider where and when you are going to play. If you aren't in a band and do not play in a large area, it would be ill advised to buy a 500 watt amp. Keep it simple and buy a practice amp, somewhere around 30 watts or so. This will give you enough volume to produce a good bit of noise when the mood strikes you, and it shouldn't drive the neighbors crazy.
If you play in a band, you will need more than the aforementioned 30 watts. For playing in a bar or similar sized location, 180 watts should be more than enough power to let your musical voice be heard. If you're considering buying a guitar amplifier with a bit more power, a half stack speaker cabinet with a decent head is a good choice.
When buying a guitar amplifier, you don't need to spend a lot of money to get quality. Crate® and Fender® both offer affordable amps with high quality sound. Research several different amplifier brands and specific models to find the one that has the required wattage and number of speakers that you are looking for and then compare prices. Many music stores offer great deals for those who are buying a guitar amplifier, but don't rule out magazines like Musician's Friend®, or online sources. There is a good chance you will find amps on clearance sale.
It is very tempting when buying a guitar amplifier to get one with all the bells and whistles, but realistically you should be able to purchase an effects processor that will meet your needs. This is not to say that added features on an amplifier are unnecessary, but they add to the cost and may not be used at all. If you are a beginner, stick to amps that are efficient. As a beginner you shouldn't need to do much more than adjust volume, bass, treble, and reverb. Make sure the amp features distortion or an overdrive switch, however, so you don't need to buy an additional pedal.