Hi Kelly,

The most common worms seen in the feces are roundworms and tapeworms. Tapeworms are small and about the size of a grain of rice while roundworms resemble spaghetti. The most common worms found in dogs are: Roundworms, Hookworms, Tapeworms, and Whipworms and Heartworms

In some cases these worms are passed from the mother to the puppy, in other cases such as tapeworms, they are contracted by other methods such as ingesting an infected flea. Most over the counter medicine will only kill one or two types of worms, so your best bet is to take a fecal sample to your vet to determine the type of worms your dog may have and then decide on treatment. Dogs should be checked for worms periodically even if they appear healthy. This is so if your pet does become ill, you are not fighting a worm infestation along with a more serious problem.

For additional information about worms, see this site
http://www.thepetcenter.com/exa/worms.html

Common dewormers are Panacur, which is a prescription product so you need to obtain it from your Vet and it works on roundworms and whipworms. Wormers labeled as Pyrantel Pamoate are the best over the counter medication for roundworms. Drontal plus is also a prescription product and is used for the treatment of Tapeworms, though dewormers with praziquantel work well against tapeworms.   Revolution and Interceptor as well as other heartworm medications also control whipworms and roundworms. Another reason to keep your dog on Heartworm medication.

I hope this information is helpful to you.