You got a great guitar but have no idea how to maintain it. Here are some helpful tips to keep the guitar looking and sounding like new.

Your guitar should be treated well. Treat it how you would treat your other valuable possessions. Never lay it down on the ground when you are not playing it or doing maintenance on it. The best place for your guitar to be is in a case, in a gig bag, on a wall hanger or on a floor stand.
Every now and then, pick it up, check for damage and polish it.
- If you have an electric guitar, try loosening the strings a bit so you can remove the dust that most likely has gathered around the pickups.
- If you have an acoustic, loosen the strings and remove the dust by the bridge.
  - You don't need to loosen them much, just enough to get a cloth underneath. *Prod the hardware to see if it's loose, and if it is, see if there's a screw you can tighten.
  - If you have a stratocaster-type of guitar, check the nut on the socket. It is probably loose, so tighten it, either just by your fingers (but it's gonna get loose again real soon) or with some pliers (don't tighten to hard, or you are gonna damage the nut).
If you're going to ever take it out of the house, then head down to your local guitar store and check prices for padded gigbags or even better, cases. Guitar cases have a hard shell that protect your instrument from damage.

Changing Strings

Restringing a guitar is not as hard as it may seem. It's actually really easy, when you know how. The thing to remember is: One string at a time.
Do not take off all strings before you put on new ones - the neck needs to have the tension provided by the strings. Start with the low E (6th string), mainly because it's at the top.
- You might find it easier to start with high E (1st string), but it's mainly all the same
A real nice thing to possess is a string winder. It makes the process of unwinding a string and winding the new one all that much easier. It's not a required tool however, but most certainly a thing I would recommend that you go out and buy, right now. First, you unwind the string at the machine head. Keep on turning the tuner until the string is so loose you can wind off the string with your hands and removing it from the machine. Then, you go down to the bridge and notice how the string is fastened there.
Make sure you have quite a few wraps around the peg for if not, the string will go out of tune more frequently and easily.
There are quite a lot of different ways that the guitar manufacturers use at the bridge. However, on most electrics it's quite simple and you don't need a tool to loosen the strings. Except if you are so lucky that you have a Floyd Rose system on it, then the strings are fastened by tightening the string into a clamp. This you need the specific tool for, but it should have been provided when you bought the guitar.

Customization

Go to your local guitar store, or look on the internet for spare parts. Replacing scratchplate or volume knobs are things almost everyone could do with their guitar.
If you are a talented artist, you can try to customize your guitar by painting it, or you can put on some stickers. However, do not paint an acoustic guitar as it can reduce the quality of the sound. Do not try to reshape it, neither the body nor the neck nor the headstock, as this can mess up the sound coming from it.