As Teejay said, play plenty of scales, they may be the poor mans shred techniques but they will get your alternate picking back. Also, I picked up a few nice tricks from Rusty Cooly (the guy is insanely fast), very basic exercises.

I stopped playing after 10 years for 5 years. After about a month or two at the most my playing to leagues ahead of anything I was able to do previously. I practised a few scales to get the fingers working again but they get boring after a while and do nothing for your creativity.

Try coming up with new complicated licks, hum the lick first, then work it out, then practise the hell out of it. Record it, then listen to it in your car for a few days untill it drives you mad. Everytime you listen to it, imagine yourself playing it exactly. After a day or so you will be literally hearing it everywhere you go. I guarantee you will be faster when you go back and pick your guitar up a few days later (this is a proven technique for learning physical movements through visualisation). It's like riding a bike, you will never forget how. After years of playing the synaptic pathways are there in your brain, you just have to reactivate them. Listen to the best players even if you don't like them: Steve Vai, Theodore Ziras, Michael Romeo, Rusty Cooly, Frank Gambale, etc., they will give you great new ideas that you never had before that you can add to your old style of playing.

Oh yeah.... then practise untill your arm burns and your fingers are raw!