I put it in my dogs water. Also, I heard somewhere (maybe on this forum) that a solution of white vinegar and water (50/50), sprayed on the dogs coat is helpful. I got the white vinegar the other day so we can try it.Apple Cider Vinegar is a much safer approach to holistic insect control for your dogs, plus it has a ton of other benefits. Look it up sometime, it's a pretty interesting thing.
I'm not buying flea meds anymore...For the last 2 years...they haven't done squat in the way of helping keep the fleas down...I'm done with them.
I've never given garlic to my dogs because of the uncertainty of safety. As for worms, I give them monthly heartworm meds...it acts as a general de-wormer as well. Eddie has only had worms once and that was when he first arrived here and Uallis has never had worms; I assume because of the meds. My cats have had worms several times though.