Even if you're fortunate enough to skip spot-scraping, sanding, and repriming, there are still some prepainting chores to attend to. They're much less laborious than removing peeling paint but no less vital to a successful job.
Rust stains on siding, overhangs, and foundations need to be removed. Leaks in gutters and downspouts have to be repaired. Loose caulking should be replaced, along with split shingles. Cracks in siding must be filled, sanded, and primed. Mildew must be scrubbed off, and steps should be taken to eliminate its return.
Also, to make painting easier, storm windows, screens, shutters, awnings, wall-mounted light fixtures (be sure to turn the power supply off), the mailbox, and even the street address numbers should be taken down, cleaned, and painted separately. You may even want to remove downspouts, as it's sometimes difficult to get a paintbrush behind them.
You can typically complete all of these preparations for an entire house in a single day or over a weekend. If you're painting a porch or an outbuilding, it may only take an hour. If you're painting with latex, you can start the following day; solvent-base paint does not adhere well to moist surfaces so wait several days until all the washed surfaces are absolutely dry before applying this type of paint.