The "drive" foot is the one you are pushing off of when making a throw so it is the same as the arm with which you make that throw. In other words, if you are right handed then your right foot is your drive foot. The other foot then is the stride foot. It is the one you are using to step into the throw. Get in the habit of driving off of that back leg. You get more power in a throw using your legs and hips properly.

i agree with mark