Alternate picking
A large part of developing the perfect Alternate Picking technique is a numbers game, and few people ever develop a good enough technique making them able to play really fast and clean alternate picking.

How to practice alternate picking
Once you are one hundred percent sure that you are playing the alternate picking correctly, you know you always without exceptions play an up stroke after playing a down stroke and vice versa and all the other little but critical elements, for example that once you go from an up stroke from a higher string to a down stroke on a lower string, that you dont hit the lower string with that up stroke which happens for a lot of people. 

Once that is down and your synchronisation is down between right and left hand you need to do the technique, the alternate picking strokes again and again thousands of times, (as you may know the ten thousand theory makes perfection) and there a few men who ever do this, but you must stay strong and stick to your guns to be fast and clean, so now check out the full video