This story covers preparing and painting exterior windows.
If you're in any doubt about whether the exterior of your home needs repainting, check the windows. Windows take a major beating from the elements and show damage and wear more quickly than other parts of the house.
Preparing windows is the same as for any other surface. Start the job in the morning, so the paint will dry by evening.
Wash the wood thoroughly with a scrub brush and mild cleaning agent (or TSP if you want to remove the gloss from the paint). Remove rotted framing members and clean mildew. Scrape loose paint and repair damaged wood. Spot-prime repaired areas and scuff-sand or degloss gloss paint. Reglaze any glass that is loose or glazing that is cracked or missing. You may have to soften the old glazing with a hair dryer, but don't use any hotter heat source -- you're likely to crack the window. Let the new glazing compound dry for about a week. Then mask off the glass at the edge of the glazing with blue painter's tape.
From 30 minutes to 1 hour for a 23-inch window, depending on the skills of the painter
3-inch tapered sash brush, putty knife, or glazier's tool
Intermediate painting skills and basic mechanical ability, careful painting and raising and lowering sashes
Wash, repair, and spot-prime surface
Glazing compound, primer, paint, masking tape
In general, paint the window from the inside out; that is, start by painting the glazing and inside edge next to the glass. Be cautious at the corners next to the glass. To avoid paint buildup (and consequent drips and sags), pull the excess paint out of the corners with the tip of a relatively dry brush.
Next paint the face of the sash -- first the boards that don't extend from one end of the window to the other (here, the horizontal rails). Then paint the boards that extend the length of the window (here, the vertical stiles). That way you won't leave crossed brush marks. Keep paint out of the stops.
Return the sashes to their proper position, but leave them short of the top and bottom by about 1 inch. Then paint the parts of the sashes you couldn't reach. Next paint the edge of the window casing and the edges and front of the stops. Don't paint the tracks unless you have removed the sashes.