The last big decision is how to apply the paint. Most pros use paint sprayers because they're fast, but in inexperienced hands a high-powered sprayer can leave drips, thin coats, and a mist that may land on many things other than your siding. If you do hire a painter who uses a sprayer, make sure he is meticulous about removing, covering, or masking off everything in the area that might get hit with overspray: gutters, roofs, windows, shrubbery, walkways, cars—you name it.
Maybe you've just moved into a new home, and you haven't got around to buying brushes and rollers yet. Perhaps you're worried that your brush-skills aren't that good, and you won't achieve that professional-looking finish that you’re really going for. Handy professionals will turn up with everything they need to get the job done, from ladders and brushes, to rollers and tarps. You just have to provide the interior paint and primer!