I have a notebook and I write their names in there, with their responsibilities to finish them before getting to do anything "fun" like TV, video games, playing outside or going anywhere, etc. They check them off when they are finished, then I go check their chores to confirm they were done properly, and if so, they get approval. If not done properly, they have to finish or start over. I made the chores not too hard, but not too easy, either (can't be done in 5 minutes). You can also reward them with special treats, like banana splits, or a movie or whatever, if you are having trouble with them doing them. (bribery works great sometimes) and it also makes it fun.
They should definitely be contributing, I agree. It will make them better people for it.