If you don't know them yet, start working on 3 note per string scales.

http://www.guitartricks.com/2000/trick.php?trick_id=3050&s_id=28

Learn em backwards and forwards for a few months and I guarantee you'll be a lot faster.

Next, try some tapping stuff.

http://www.guitartricks.com/2000/trick.php?trick_id=1873&s_id=13

Even if you don't like tapping, just learn the beginner stuff. It forces you to speed up your left hand... especially your pinky finger... because almost everything is using hammer-ons and pull-offs at a greater speed than you'd play while picking.

Lastly, learn a bunch of little 'tricks' that make you sound faster than you actually are, like pulling off to open notes. Most of the instructors on this site have a ton of little 'secret' riffs they use just to freak people out.

http://www.guitartricks.com/2000/trick.php?trick_id=1653