Why is important to tune your guitar?
The most simple answer is to have a good sound of the guitar. Have you every played an electric guitar witch is out of tune, distortion turned up and you let a power chord ring out. It sounded horrible. Now that's why you should tune your guitar every time when you play. Another important aspect is that a well tuned guitar will help you develop your hearing skill faster.
How to tune a guitar?
Well, the easiest way is to buy a tuner and use it to help you tune in your guitar. But if you want to use your ears to tune your guitar (which i recommend) use an online guitar tuner, like this;
Guitar Tuner courtesy of the folks at Wimpy Player
This tuner has pretty much everything you ever needed. The only flaw i can find in it is that the first string on the tuner is the low E. I thought the low E string is the 6th string, but who cares? The tuner besides that is epic. If you select the Tone mod it will give you an epic never ending mmmmm sound. This is a lot of help for everyone.
Okay now let's get down to the real tuning part. On the headstock you have your Tuning pegs. Turn them counter-clockwise will make a higher pitch, turn them clockwise will make a lower pitch.
Tuning a guitar with a Floyd Rose Tremolo System
I have an Ibanez GRG270B with a Floyd Rose tremolo system, and it's pretty much a pain in the ass to tune it fast. After a time a kinda got a "fast" way to tune it. You should know that your bridge have to be parallel to the guitar's body. To do this, i suggest you to push down your tremolo, really hard, place something between the bridge and the body, then tighten the springs at the back of the guitar. After that start to tune your guitar. After you tuned it in remove the stuff witch is between the bridge and the body and there you have it. If when you tune your guitar and your tremolo isn't parallel to the body, tighten the springs even more.
This should be done only one time. For the next time remove the locking nut, tune every string ut a bit then start to tune them down. Start with the 1st string. You may need to recheck it many times before it get tuned well but don't give up. You will get it eventually.
So that's all for today, try to use you ear when you tune your guitar - Floyd Rose users: i don't recommend to use your ear, it's pretty much work to do it with a tuner - and have fun. One last tip. Play a little before you tune your guitar. like a few chords, to warm up your string so they won't be detuned.