Even great paint won’t stick on a house very long if the surface is not properly prepared before it’s applied, so a little extra work upfront will save lots of work later. Paint won’t stick well on dirty surfaces, so the first order of business is cleaning.
Trisodium phosphate mixed with water makes a great cleaner for painted surfaces, but be sure you rinse it well with a garden hose or a pressure washer. Any paint that’s bubbled or cracked needs to go, so some sanding and scraping may be necessary.
If you expose the bare wood you’ll want to apply a coat exterior primer over those areas so the topcoat will stick properly. Finally, apply some quality latex caulk to all the gaps or cracks. And once it dries, you’re ready to paint.