Frontline can be used from 2 days old (spray) or 8 weeks (pipettes). Definitely the best for treatment of fleas. can be used every 2 months, but every month if they have ticks as well. Dont bath your dog the day before or the day after application.
I use Frontline also. I agree with Stephy about the flea collars, I would stay far away from those. See what your vet recommends and get your stuff there. Avoid all the grocery store/walmart products, like Hartz, for example - they can be dangerous.
Yes I too am a Frontline user and I agree with the others about not using flea collars ( I have seen dogs have reactions to them and lose their hair in the region where the collar touched:-( ) I also agree with not using any store bought flea remedies no matter how much better the cost is, there are horror stories all over the internet with almost all of those products:-( Its best to get your products from the vets office or from a reputable source.
I use a prescription medicine, Sentinel, that I get from my vet. It does heartworm, intestinal worms, and fleas, but not ticks. It's given as a once a month pill, a tasty pill so there's no fight getting it down. I do have to cut the pill up since Boop won't chew it. Downside - it's pricey, about $10/pill. I don't know how that compares to Frontline.
Frontline doesn't work at all on my boys. K-9 Advantix did though. Now I don't use the chemicals. I make their biscuits and put brewers yeast and garlic in them and it's worked wonders and they love the biscuits.