Exterior paint is protection as much as looks — it shields siding and trim from sun and water. Because it faces the weather, prep and timing matter even more than indoors.
Prep and repair
Scrape loose and peeling paint, sand rough edges, and wash off dirt and chalking (with caution on older homes that may have lead paint). Replace rotted wood and caulk gaps before painting.
Watch the weather
Paint in dry, mild weather — not in direct hot sun, not when rain is coming, and not when it's too cold to cure. Damp surfaces and extreme temperatures cause peeling and poor adhesion.
Prime and use quality paint
Prime bare wood and repairs. Use a quality exterior paint rated for your surface; cheaping out here means repainting years sooner. Two coats over primer give the best protection and colour.