How to play guitar like a boss

If you're learning how to play guitar, the most important thing to acquire first is accuracy, and with accuracy, the speed will come very easily.

And when I say slowly, I mean real slow, starting at 60bpm, and then making your way up to double the speed of the original line you're playing (but not if you can't play it without timing issues). You need to be able to play it flawlessly first, maybe whitout even looking at the fretboard.
Then, when you think you mastered it at 60bpm, (to the point were you don't make any effort playing it and it's almost natural) start rising the bpm for every 1 to 5 minutes you play the line. Whenever you feel tension while playing at a certain bpm, that means it's the fastest you can play accurately. When that happens, you should stick to a lower bpm for some time, and try it again later. It's that simple, you just need a lot of patience, since it might take 2 days to learn a single line perfectly.

I found another blog post about this, here's the link: http://lorinator.feminoise.com/the-real-secret-to-playing-fast/