I've had a lot of problems getting rid of fleas until I started using Fleas Off as well as using Advocate once a month.
Fleas Off is a natural flea way to control fleas. It contains sterile water, vinegar, garlic, citrus, and herbs. I add a teaspoon to his dry food every day to naturally prevent fleas from biting and laying their eggs.
Both are brilliant products to treat your cat against things that move in the grass! But you still have to check for ticks and parasites - and if you do find a tick - rush your pet to the vet immediately.
I've also used apple cider vinegar, which actually prevents the fleas from biting. While it doesn't prevent fleas, it does prevent biting (although it does smell very strong!) I actually dilute the apple cider vinegar in water and then cover his fur with a damp cloth - this usually lasts a few days. (And it is not a tried and tested method - it just stopped the constant biting!)
Have your pet checked at least once a year and if you see any problems, strange bites or marks, or if your pet is behaving strangely (drinking too much, scratching incessantly, not eating, showing any signs of distress or acting extremely cranky) - take your pet to the vet as soon as possible.