I enjoy playn´ chromatic scales ´cause they are pretty basic and you can speed ´em up. I use ´em for warm up but also in solos and I practice them them usualy. Inspiration of chromatic scale came to me after watching Petruccis video. I like the way he´s foolin around (like he can´t make it over 220 bpm). I usualy start playng chromatic at 180 bpm and then I increase the tempo by 10 bpm all the way up till 250 wich is quite fast.

Playn´ chromatic scales will not only help you to increase your speed, it will also help you to synchronize you left and right hand wich is really important.

So, find some chromatic scales and metronome and dig in.

Another thing that is good for speed is 3 notes per string scales. Just listen to players like Petrucci, Malmsteen, Gilbert and Morse. They use it all the time. However, it´s harder to fix speed on these ones compare to chromatic scales ´cause you fingers will probaly be forced to change positions and so on. Let´s say that between 120-145 bpm is a great speed for 16-note triplets wich are very useful and they sound better than a chromatic scale.

One more thing. I just don´t know how Yngwie can play that fast by only using his wrist. It´s impossible. Usualy, when i play slow things I use only my wrist but when it comes to faster, I just got to use my elbow and stick out my point finger so that I only hold my pick with thumb and f**k you finger. Is it a right method. (I know that Petrucci does so)