Sure, you're probably going to sign some sort of agreement that the contractor will work for a certain fee, but simply discussing a project at length is no guarantee of the kind of work you'll end up with. In the contract, have the details of the project carefully spelled out. What dates will they start? How long will it take? What permits are required to be pulled? And what, exactly, are you looking for in the project?
There should be a clause for dealing with potential change orders, which allow for additional projects to be carried out at the homeowner's or contractor's behest. In addition, if you want to make sure that your home improvement professionals clean up after themselves when they're done, be sure to include a broom clause in the contract, which legally requires them to do so.
It doesn't hurt to put a liability release in writing and to make careful note of the materials that will be used, which will also allow you to see where your budget is being spent. And when it comes to budget, check out the next page for another important financial question for your contractor.