Trying vegetarian, which common ingredients do I avoid?

I'm trying vegetarian + fish/seafood (don't know what to call that) and I've been doing it for about a week now. I've been checking labels, but don't have a clue what most of it means. I know things like lard and gelatin are common and should be avoided, what are some others to stay away from? I've looked online but I keep coming up with vegan, and that's much more strict than I want.