Originally Posted by: IWannaPlayFastI'm 15 years old ...

It's a good thing you are so young. You probably have more leisure time at your disposal to put in the necessary practice time in order to "play fast".

I did a few tutorials on speed building:
http://www.guitartricks.com/tutorial.php?input=213
http://www.guitartricks.com/tutorial.php?input=287
http://www.guitartricks.com/tutorial.php?input=211

And the amount you will have to practice is exactly what all the other GT people have replied: a lot. An awful lot.

In the long run most of playing fast is much easier than many people imagine, it simply comes down to putting in the time to do it right. :) Happy playing.