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 house bath may reveal nails that have popped out of the siding or rusting nail heads that have left streaks of rust on exterior walls. If so, use sandpaper or steel wool to clean the nail heads. On clapboard siding, use a nail set to recess the nail head about ⅛ inch below the surface of the wood. Dab on a coat of rust-inhibiting primer (unless the nail is aluminum or nonrusting galvanized steel), and let it dry. Then fill the nail hole with spackle or putty. When the filler is dry, give it a coat of primer. For flathead nails, which cannot be recessed, sand the heads until they're shiny, and coat with primer.
My painter franchisee, who I got from Angie's List, must have found some shmucks on the corner to paint my house. I specifically said I wanted stain. First my house was painted the wrong color, Then it was painted with LATEX paint- not stain. Estimates to 'undo' the damage is around $10,000 and its not a guarantee that it will work. The work is at best amateurish. Many underpainted or not painted spots, drips, etc. They did the entire outside (scraping?, priming? caulking?, painting), cleaned up and left within the time I left for work and came home. There were thee of them (my neighbor told me) This was two years ago and I am still upset. Can't be fixed.