They are probably fungus gnats or white fly's. I had them here are some things you can do. Sand is great. mix soil with half sand it allows for good drainage. Add about an inch to a half of pure sand at the top of soil. That is where the gnats live and it ruins the "ideal conditions" for their survival. Allow your plants drying out periods before waterings. Plants need plenty of light. gnats like dark, damp conditions.
Never plant in yellow containers, it attracts the gnats. Clay pots are porous so they are the best for air circulation.

They sell yellow sticky strips to get rid of them also spray them with a little dawn soap and water in the flight stops them instantly.

Another tip is to check your kitchens and bathrooms. Dry foods, bread, fruit and sinks are all places they hide and lay eggs.

Good luck.

*here is a link that will help:

http://www.doityourself.com/stry/fungusgnats