I know the dosage and whatnot is different for dogs, but we buy Frontline Plus for our cats from the vets. I've looked online at like petmeds.com but it was the same dang price. I strongly suggest avoiding anything "over the counter." They simply do not work the same, the dosage can be for the wrong animal size, and some of them are just plain dangerous. Make sure you get the right dosage. A small dog takes less medicine than a st. bernard. This is where the vet comes in handy again.
As for where to put it, there is a specified place for most meds - which is behind the neck, sort of in between the shoulder blades. This is to prevent the pet licking the medicine off, which can be both dangerous and a waste of money.
