It is crucial to carry out appropriate due diligence. Ask questions that will uncover things that may pose a risk to your reputation. For example, how do they handle client complaints?
You could oblige them to comply with a code of conduct. In this way you can ensure that your standards are upheld and you could include a clause on dispute resolution.
You could include specific clauses in a set of terms and conditions. However you must beware of ‘liquidated damages provisions’, where a penalty is payable for example for late completion. These should only be used as a genuine pre-estimate of losses which will be suffered by a breach of the contract and not used as a penalty clause, otherwise the provisions may be held to be unenforceable.