Limit your down payment or deposit. A good rule of thumb is an initial deposit of no more than 10% down or $1,000, whichever is less. Unless the job requires custom-made items or special orders, in which case an initial down payment should be no more than 30% of the total value of the contract.
Licensed contractors are required by law to provide a written contract for residential work, signed by both parties. Don't rely on verbal agreements. Get all guarantees, warranties, and promises in writing. Limit your down payment or deposit.