Flea preventative?

Just wondering what, if any flea preventative is a good one. The daycare we're going to take Helix to has it on its list of requirements, so I thought I'd do some research :) TIA

Garlic!!!! I am an advocate of garlic since I've tried it and have been flea free since!!

http://dogs.about.com/cs/disableddogs/p/fleas.htm