Your first clues about a prospective contractor are how they respond to your initial call. There is nothing wrong with them answering their cell phone but that should not be their only means of communicating. A contractor should have an office number and an email address. A fax number and a web site are also a plus.
A lot of this is of course based on the size of the job. If they are just straightening a loose mailbox then a handy-person that works out of their truck just using a cell phone may be all right. The danger here is once they are in your home you may be tempted to give them work that is more involved.
Never accept a verbal agreement for work that is going to be more then the simplest of jobs. Even then, major damage can be caused while doing minor work.
All jobs should be written up on a contract showing the contractors company name. Their business license and contractor’s license numbers should be on the contract. There should also be a statement with their general and liability insurance numbers and the name of their insurer. A start and finish date should be included in the contract.
There should be no request for a partial payment until materials have been delivered to the job and or some work has been done. If permits are needed, they should be displayed on site before any partial payment is made. All of this written on a sheet of notebook paper and handed to you piecemeal should be a warning and a possible foreshadowing of their quality of work.
The contract should state that necessary permits and inspections will be obtained and handled by the contractor. Payment for these should be by them, and their cost should be included in the general cost of the job. If they can’t afford to pay for these up front then you should not use that contractor.
Warning signs that you may have the wrong contractor for your home repair project are more than just a bad feeling. If any of these items are missing, do not accept them promising to give you the documents later. No matter how nice a contractor may seem all of these items are needed to do business professionally.