To paint double-hung windows, you'll want to remove them from their frames. Newer, spring-mounted windows are released by pushing against the frame. If you have an older window, consider painting it in place.

Drill holes and insert two nails into the legs of a wooden stepladder, and mount the window easel-style for easy painting. Or, lay the window flat on a bench or sawhorses. Don't paint the sides or the bottom of the sashes.

Using a tapered sash brush, begin by painting the wood next to the glass. Use the narrow edge of brush, and overlap paint onto the glass to create a weather tight seal.

Clean any excess paint off the glass with a putty knife wrapped in a clean cloth. Rewrap the knife often so that you always wipe with a clean piece of fabric. Overlap the paint onto the glass about 1/16 of an inch to create a good seal.

Paint the flat portions of the sashes, then the case moldings, the sill and the apron. Use slow, careful brush strokes. If you're painting with the sash in place, you'll want to avoid getting paint between the sash and frame. For casement windows, open them up completely before painting.