Here is what I use (taking a more natural approach because I've heard of lots of reactions to the applicator medicines... and have heard that in certain places the fleas are actually becoming immune to certain applications):

-A nice spray down of Cedarcide before going to where I KNOW there will be fleas. This stuff is killer. It is a cedar oil that suffocates the fleas (or other bugs for that matter... good to have around in case there is a spider LoL)
-Neem oil mix (you can use straight neem oil, lemon, and water and mix that) to spray over her to make her smell good/add a little preventative.
-I used to use Bug Off Garlic (I would recommend the pills) but I had the powder and it just smelled too bad after awhile. Lol So the pills smell less.

And the most important, I think, is a good diet. Delta has never had a drop of flea preventative except for what is above and she's never had a flea.

There are a few different applications such as Revolution (which includes a heartworm preventative), Advantage, Advantix, Frontline, Frontline Plus

Buffalo, I believe, has bad deer ticks which carry lyme disease... but I don't know about fleas. I would research lyme disease and look at pictures of a typical 'bullseye' that appears where they were bit by a deer tick with lyme disease.