The root of most claims comes from having no contract, a poor contract or contract that no one pays attention to. Make yourself available to the contractor, especially on the first day. Talk to your contractor during the project being careful not to appear overbearing. Open communication will alleviate the opportunity for discrepancies. Document all communications.
Life is full of changes.
If there are changes in the plans or the contract that occur during the project, put them in writing as amendments to the contract, including the changes in the project cost. Properly executed change orders can reduce misunderstandings and cost overruns. Change orders should be signed by both the homeowner and the contractor. When possible document and or recap all conversations in writing or email. Keep a log of all conversations and copies of all documents, correspondence, canceled checks, change orders, receipts, etc.