What is the best workout for getting nice abs?

I’m not concerned about arms, legs, pecs etc, but the ol’ gut is getting bigger as time goes on. What’s the best way to lose it, and to tone the abs?
I know that crunches build the muscle, but I’m also wondering how to lose the fat.
What’s the best way to do this?
How about something that I don’t have to pay for
I don’t want to go buy a book to tell me what to do, that’s why I’m asking on here