When buying an instrument it is best to check out which guitar dealers have a good reputation, you don't want to get ripped off.
Shop around. Do not buy the first great instrument you see.
Buy an instrument that suits your style of music. Salesmen can help you find an instrument that is suitable.
When buying second-hand make sure you check for bumps and scrapes. Look around the frets for rough patches and look down the neck to check for any curves and buckles.
Second-hand guitar shops are more expensive than other second-hand sources but guitar shops sometimes offer a guarantee that makes it more worthwhile. When buying second-hand amps, check whether it is a valve amp. The valves in valve amps get worn out and can cause a horrible sounding tone. Ask about the amps age and use your ears to see how it sounds. Also ask about replacing the valves.
If you are planning to gig, get a carry case or gig bag. Make sure your gig bag is padded and water proof.
Guitars that are made by well-known companies are worth more second-hand. You may want to keep this in mind if you plan to sell a guitar that you are about to buy.
Buying an expensive instrument can be a waste of money if you don't stick to your hobbies. But if you know guitar playing is a hobby for you then you may want to buy the best instrument in your price range. Pricey instruments tend to sound better which makes playing guitar much more enjoyable. And if you sound bad, you'll know it's not the guitars fault.
When buying amps it is good to follow similar guidelines to buying guitar. Make sure it suits your style of music.
If you want a powerful amp, don't go too powerful. Powerful amps need to be at high volumes before the distortion reaches top quality. Find one big enough for the type of gigs you play, but not too much bigger.
Guitar effects and pedals can provide the extra distortion if you are having trouble with your amps distortion.
For those who cannot practice loud but want to, try headphone amps or small, beginner amps. Get one with reverb or chorus to cover up any poor quality associated with cheap amps.
Keep your guitar away from water and any sources of heat. Guitars are very sensitive to heat and some guitars use water-soluble glue.