Here's what I've done to improve speed, and it's done wonders:

- Practice regularly, even if it's just 10-15 minutes a day

- Minimize hand and finger movement. Notice how all the fast guitarists make it seem so effortless? That's because they're so efficient in their movements that it is.

- Keep relaxed, and keep your hand relaxed. Tension slows you down.

- Scales give you a excellent finger workout, and take the work out of finding what notes sound good. It's by far the easier road to take then being musically inexperienced, where you have to learn the same things the hard way.

- Learn the scales slowly until you can play them blindly. Forwards and backwards.

- Try playing the scales in 'triplet' form, forwards and backwards.

- Once triplets become second nature, practice 'sweeping' your scales.

- Start slowly and precisely and build up speed over time. If you find you're playing sloppily, then slow down. Being slow and well is far better then playing badly - anyone can bash strings.

- Practice, and practice again. It's muscle memory that you rely on, and you're training that.

Speed is achieved by coordinating the right and the left hand. There are many exercises to do this, but playing a chromatic scale can work wonders. Do it very slowly at first using different combinations of the fingers 1234, for example, 4312, 1432, etc. There are many combinations. Practice them slowly and with a light touch making sure to coordinate both hands perfectly. Then practice them with a bit of speed. Remember, speed has nothing to do with tention, although it does sometimes want to cause it. You must be very relaxed and your hands have to be extremely relaxed. The coordination and speed come from your mind, not from your fingers exactly. I hope that makes sense and help you along.

The only possible way to increase speed is by practicing. Also try playing this over and over again and it strenghthens your fingers, and stretches them out.

I say take the peice your trying to learn real slow at first and then when you feel you got it go faster and faster till you can do it perfectly. And the main thing is practice.