what is the best over the counter dewormer for dogs?

There are NO good over-the-counter wormers. And its incredibly irresponsible to want to worm a dog without even knowing whether or not they have worms and if so, what kind.

Get your dog and a fresh stool sample to the vet so the vet can prescribe the CORRECT wormer if your dog has worms.

Pumping useless and potentially dangerous chemicals into a dog's body is never a good idea.

There is no all-purpose dewomer that worms for everything...including at the vets.

By the way, over-the-counter dewomers often contain tolulene which is very bad for the pet's liver. Read labels carefully.

The proper thing to do is to have your pet properly diagnosed by taking the vet a poop sample and then getting the correct medication for any specific parasites your pet has.

I would not use one of those but take a fresh poo sample to the vet and get something that they tell you to use.

None. OTC products don't work, may harm and even kill your dog.

Take the dog and a fresh fecal specimen to a vet for a proper diagnosis/treatment.

There is NO good OTC wormer for Tapeworms. Round worms ENCYST in tissues IN the puppy (unlike other types of worms) once they transfer over IN the mother's milk, so even if you worm the puppy (many will never be touched). Round worms require many rounds of worming by a QUALITY product (and subsequent fecal testing) & (in my vet's opinion) are the CAUSE of hiccups in puppies - when some hatch, & begin to MIGRATE.

There is no good OTC wormer for tapeworms. Pyrantel paomate works for most other intestinal worms

Piperazene is the generic ingredient in roundworm treatment, but it wont touch tapeworm. Sherleys make a reasonably safe and effective roundworm and tapeworm OTC treatment, its ok to use this if you alternate with visits to the vet.
It comes with two different types of tablet. You use them two weeks apart, and the dose is based on your dogs weight.

Here is a chart , if that will help.

http://www.drsfostersmith.com/pic/article.cfm?articleid=1086