We use natural consequences. Natural consequences would be, if you break a toy, you have to do chores to earn the money for the value of the toy (and still don't get a replacement), or if you don't complete your homework because you were playing soccer, then no soccer for 2 days. We also pick our battles.
My 9 year old son tonight who is usually very good with homework flat out refused. I said that's fine.. U dint have to do it but then no tv, no Legos, no games, no Wii, etc. and he said why?? And I said all of those things you earn on a daily basis because you're a great kid and you do what's expected of you. But if you don't and don't take care of your responsibilities then you didn't earn those things. Those things are bonuses not a right.