How do YOU effectively discipline?

Ok so I am asking for input here. How do you effectively discipline your children?? I have an 11-yo son that has become terror at school and I am at my wits end trying to get him to do right. He talks back to the teachers, he walks away from the class and goes somewhere else (which is considered skipping class) and he misbehaves on the bus. Last week he was suspended from school for 2 days because of skipping class. For those days (and even other days as well) he was made to work. He helped my mom out for 2 days and then my mother in law for another day around the houses. All the other kids went camping with my sister and brother in law and he had to stay home, he has not been allowed to ride his dirt bike, and he has watched very little tv. Then his first day back to school he gets called to the office and has been suspended from the bus for 5 days because of standing on the bus...this happened before he was suspneded from school not on his first day back. He smiles and seems to think that it is funny and the punishments have not seemed to phase him at all. I really thought once we got the dirt bike(we have only had it about 2 weeks) then he would start behaving because he loves to ride it! But so far he has done without.
What I am in desperate need of is some advice from all you wonderful blogging mommies (and daddies) out there. What have you done that worked as far as punishment? All that we have done to punish him has not seemed to work. He is a little big for spankings. What else can I do???