That's a pretty generic goal, so I'm curious what your training actually looks like. Also curious about your current stats (height, weight, current fat level). If you have a bunch of fat to lose, it isn't a case of "more ab work means better abs."
Like Yogi said, simple is fine. Without knowing what your current training is, I'd superset a plank variation with something in your workout one day a week and superset a crunch variation with something in your workout another day.