Light biting by a kitten is totally normal...they are 'tasting' their new environment. The same with chasing your feet and hands..it is all play with them.
It's when they are older, after their baby teeth have fallen out, they actually start stalking your hands, feet, etc. By the age of about 6 months..all biting should stop. After than it can be hard to stop the behaviour.
It's trying to find the trigger to their biting that can be the problem. Sometimes a cat is just plain aggressive...and will never stop biting. I wouldn't like to always live in fear of being bitten. What kind of relationship is that with your cat? Some cats will stop after a few strict sessions on what is acceptable and what is not.
Really, accept chewing and chasing up to about 4 months...after that start being a little stern with them if they bite. Remove your hand, foot, etc...or simply get up and walk away. When they play without biting..really praise them and let them know that non-biting play is totally acceptable. Let them bite toys..perhaps their teeth are bothering them. If they open their mouth to bite....stick a soft toy in their mouth. It does work...I've done it. Not one of my kittens bite now....wouldn't even think of it. They may bite, gently, each other, but never me.
If they still want to bite..try playing away from your body...get a long stick with feathers, etc, or a laser pointer..in other words...you two are playing, but are separated from each other.
If they attack you while you're doing nothing..you have a problem. They are hunting, and stalking you. Again, I would try playing at a distance with them. Perhaps there are behaviour books that give some better tips.