Buying your first amp can be either a good or bad experience. Cheap practice amps with 8" speakers and low wattage will often be a waste of money and time invested in nothing more than poor tone and months of uninspired practice sessions. It's far better to buy a good quality amp with decent tone that will inspire you to play day and night for months and weeks to come. below is a short list of what to keep in mind for that first amp purchase.

Tube, Solid-State or Digital?
While tube technology is still considered as the warmest and most pure for tone, these days many of the solid-state amps will offer us excellent tone, (i.e., the Peavey Bandit),  for a lot fewer bucks, (and with far fewer maintenance headaches). However, tube tone is still considered the standard by many top players. Take a blind listening test, and let your ears be the judge. But, remember that tube tone will likely cost you 2x what solid state can provide. As far as digital amps, keep in mind your sound is being passed through a computer before reaching that speaker, so be careful and spend time trying out several digital amps before buying one, (if digital is of interest to you). The advantage to digital is the vast selection of built in present sound-banks. There may be a lot of selection, however it may come at a loss for quality of the pure and natural tone of the instrument.

Size 
A 100-watt stack is overkill if you live in an apartment and need an amp only for home recording /practice. Conversely, a 10-watt combo is woefully inadequate if you play in a band with a solid hitting drummer, and will likely have a pathetic 8" speaker delivering terrible tone. Choose an amp that’s right for your primary application. You’ll need at least 30 watts for playing live with a rock band, but smaller amps often provide surprisingly huge sounds in the studio—just ask Jimmy Page. Also, as a rule of thumb, if you're playing out often, you might want to shoot for at least 15 watts of tube tone, or 80 watts of solid state and above all else always go for an amp with the standard 12" speaker. Even though the 10" speakers can offer a decent sound for at home jams, when compared to the standard 12" speaker, 10's just can't match the overall quality of guitar tone.

The Power-amp /Pre-amp Section
Distortion is usually generated by three distinct sources: the power amp, the preamp and the speakers. Many players overlook power amp distortion when trying an amp, but the power amp section is the source of what guitarists describe as low-end chunk. Audition the power amp by turning the master volume way up and turning down the gain. The sound should be lively, with a crisp attack.


Distortion /Overdrive
Preamp, or gain, controls (sometimes called “volume” on master volume–equipped amps) let you dial in impressive-sounding distortion at low volumes, but excessive preamp distortion can sound too compressed and sizzling at high volumes. Turn down the gain and crank up the master volume until the amp is set at the output level you’d normally play at. Now, slowly increase the gain until the sound becomes as distorted as you want it to be. If the tone is buzzy and lacks dynamics, the amp's over-driven tone will horribly fail on stage!

Crunch
Over-driven speakers create one of the most desirable distortion characteristics: crunch. The best way to test for this is to dial in a clean setting and turn the volume way up. Low-wattage speakers break up at lower volumes, but they have a tendency to turn to mush at excessive volume levels; high-wattage speakers may not break up at all. Choose a speaker that sounds lively, defined and harmonically rich at volume and distortion levels you’ll normally play at.This is where you'll hear a drastic difference between those 8" and 10" speakers compared to the standard 12" speakers sound.

More About Speakers
While often overlooked, the speakers are an amp’s most crucial component—they’re the last thing standing between all that electronic gobbledygook and the sound that reaches your ears. Different sized speakers have different tonal characteristics, and you should consider speaker sizes the same way you’d consider an amp’s wattage rating. Speakers are like booty—small ones are tighter and big ones have more bottom end. But like a pair of pants, cabinet design can shape bottom end as well. Which is why a closed-back 4x10 cabinet may put out slightly more bass than a 12-inch speaker in an open-back cabinet. Typically however, most first time amp buyers aren't spending the kind of money ($450.00 and up, and you'd be responsible for closing the back at home), that would buy them a 2x10 cabinet amp with a closed-back! So, as stated earlier, go for the 12" speaker!


Digital Channel Surfing
Multichannel digital amps are great for players who enjoy flipping through a lot of different tones, but if all you want is a good clean sound and a good distorted sound, they may be more amp than you need. If you decide that a digital amp with three or more channels and dozens of pre-sets is right for you, look for one that provides separate EQ controls for each channel, and lot's of flexibility with adjusting the effects of each digital pre-set. Also, keep in mind one of the biggest complaints regarding the digital amp world is that they seldom, if ever, will have a nice basic pure clean tone! The digital amps are running every setting through a patch-work of computer processors and even the cleanest digital tone will, ...well still probably sound digital in one way or another compared to a solid-state or tube amp.

Twist Some Knobs
You should be able to dial in a sound you like quickly and easily. Adjust each tone control and take note how they interact with each other. If it’s too hard to dial in a decent tone in the store, chances are you won’t be able to when you get the amp home, to the jam-space, or onstage.

Additional Features
While tone and volume should be your foremost considerations, you should also determine what extra features you really need. Built-in effects are great if you want a no-hassle, all-in-one package, but they may not be as flexible as external effects pedals and processors. An effect loop is useful for effects like digital reverb and delay, but it’s not essential if your effects consists of a few stomp boxes. Line outputs with speaker emulation are helpful for home recording, and external speaker outputs are great for expanding your live rig. Bottom line: don’t pay extra for features you’ll never use.generally less is more.

Well that about wraps-up this break-down for first time amp buyers. And, while it's important to keep things like your price point in mind, you also need to remember that you want the best tone money can buy in that price range. This might require the sacrifice of some bells and whistles in respect for that tone quality. But, I've always found that starting out with the best tone you can afford always wins down the road.