Not only careful communication is essential, but we would greatly recommend, when you pick out your type and brand of paint that you go and pay for it, with the contractor's discount, which is given by Sherwin-Williams and most paint companies. Then you will know how much paint you purchased and the coverage. If it is possible, inspect the work of the painter daily.
Once work begins, hold brief daily meetings to discuss the job and schedule and quash any misunderstandings. If there are surprises, seek middle ground. No contract can anticipate every possibility. Materials may be unavailable. Large chunks of rotten siding may crumble along with the old paint. Exterior jobs may be stopped cold by a week of steady rain. But know that you'll pay extra if you change your mind about a color after the trim is already painted or otherwise add tasks to the project.
The Lead Renovation, Repair and Painting (RRP) Rule establishes requirements for firms and individuals performing renovations, and affects contractors, property managers, and others who disturb painted surfaces. It applies to work in houses, apartments, and child-occupied facilities (such as schools and day-care centers) built before 1978. It includes pre-renovation education requirements as well as training, firm certification, and work practice requirements.