If you aren't satisfied with the work your contractor is providing, sit down with him to discuss the situation. Point out specific items in the contract that he is failing to uphold. When you notice a lack of competency or actions that go against the contract, write them down and take photos as documentation. Present these facts when you meet with him. If you don't feel comfortable talking with him yourself, an attorney or arbitrator can help you with the meeting.
Terminate the Contract
If the contractor makes it clear he is unable or unwilling to correct his work to your standards, try to terminate the contract. If you have a binding contract with him, you may find it difficult to get out of it. One potential difficulty is his right to take you to court for a breach of contract. In this case, the burden of proof falls on you to show that he didn't live up to his end of the contract. This is where your photos and written documentation are useful.
Take Legal Action
Read the fine print on the contract to determine if it includes a binding arbitration clause. This means you agreed to handle disputes with the contract through an arbitration process. If your contract doesn't include it, file a suit in small claims court. Keep in mind the monetary rewards are limited in small claims court. The cap depends on the state you live in. If you aren't sure how to proceed with a legal action, consider hiring an attorney with experience in construction contracts. He is able to review the case, identify loopholes in your favor, identify potential difficulties in your case and recommend your next step.
Report the Contractor
Whether or not you take legal action against the contractor, you have the option to file complaints to various agencies. Start with a complaint to the Better Business Bureau. Also, report him to your state's Department of Consumer Affairs. If you leave negative online reviews about the contractor, only include facts without embellishing or making personal attacks. This reduces the chances of being sued for libel.