How much PDA is too much PDA?

I don't want to be "that one couple" that sits and makes out everywhere, so I need to know...how much is too much? Not that we make out in public, but when we're sitting in a grocery store or somewhere else public, is hugging too much even? Where is the line drawn? I love being with my girlfriend and all, and i'm not afraid to show affection, I just don't want to go to that level...