Get either Advantage or Frontline Plus. My vet says if you try one and it doesn't work, try the other. I used Frontline Plus and it didn't work but have had good luck with Advantage. It's easy to use. Just part the hair on the back of the neck and put it in the part. This protects against future fleas. To get rid of the active fleas right now, there is a pill to give them. I can't remember the name but your vet will know. Within 1/2 hour, the fleas drop off them. It doesn't keep them off -- that's why you also use the Advantage or Frontline Plus. Then, vacuum your house and spray a flea spray. Get rid of the vacuum bag. Spraying can be tricky when there are cats in the house. You'll have to put the cats in a separate room. However, my vet sold me a spray that the cats can return to the rest of the house in about 1 hour. This method helped when I had an infestation.