If there is any peeling — and there usually is somewhere — it's essential to scrape off any loose paint. This doesn't just mean the parts that are already separated from the wood and ready to fall off on their own. Each spot where paint has peeled loose needs to be scraped thoroughly until you can no longer get the sharp corner of a putty knife under any of the surrounding edges of paint. Then, the bare spot needs to be sanded until the paint edges are smooth.
For interior jobs, make sure you've cleaned all of the awkward spots, including behind the toilet, and picked up any knickknacks that might get in the way (e.g., soap containers, loofahs, and kitchen organizers). Removing the switch plates and outlet covers from the walls also goes a long way toward speeding up painting time—and painters' time is (your) money.
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.
The best time of the year to paint your home is typically in late spring and early summer when it’s warm outside and moisture is low. This can change based on your geographic location. For example, fall can be a good time to paint in California when the difference between high and low temperatures is low. Your painter will select the optimal time to start your exterior painting project.