Start by thoroughly examining the outside of the house or outbuilding -- not just the exterior walls but under the eaves, around windows and doors, and along the foundation. Look for split shingles and siding, popped nails, peeling or blistering paint, mildew, and rust stains. Once you've identified the areas that need attention, roll up your sleeves and make the repairs.
Here is where this affects you as a consumer. You select a painter with a contract that says 2 coats, $500 down. You give the company the deposit and pick your colors a couple of days before the project starts. The painter goes to the store with your colors and figures out they are deep base. He (or she) not only needs to charge you more for the paint, but he also needs to charge you for a dark gray primer coat. Ninety nine percent of the time that primer coat is going to be really, really expensive since you already gave a deposit.