I use Advantage II, It prevents heartworm, fleas, hookworm, roundworm, and whipworm. It does not work on ticks but those are not a problem where I am.
On past dogs I've used Heartguard, Interceptor, Frontline, and Advantix II. The first two are heartworm preventatives, but both have stopped being effective where I am and I actually had my elderly dog turn up positive for heartworm after being on Interceptor for years. The second two prevent fleas, and Advantix also prevents ticks. Frontline is no longer effective where I live and I've found fleas on my dog three days after using it. My current vet no longer even bothers carrying Heartguard, Interceptor, or Frontline due to their ineffectiveness.
Talk to your vet, and other pet owners in your area, about which preventative is still effective where you live, I live in E. Texas and that's where I had the Interceptor fail, and I've also lived in New Orleans which is where i found the Frontline to be ineffective.