How to get a contractor to meet their timeliness?

[Scott K.]

I've had so much trouble getting contractors to just get CLOSE to what their job time line estimates were. Any tricks or ideas to put into a contract to incentivize a realistic time line? Some kind of money incentive? Some kind of legally binding contract? How do you do this without pissing off the contractor, or making them simply disappear if they go over the time frame?