Vacuum your wooden window frames and sills using a hose attachment. Remove all loose dirt, dust and debris.
Fill a medium-sized bowl or bucket with warm water. Add a few drops of a mild dish soap. Use your fingers to mix the soap and water together until bubbles form.
Submerge a sponge into the soapy water. Take the sponge out of the water and wring it out so it is moist, not saturated. Wipe the window frames and sill down with the sponge. Rewet and wring the sponge as needed to keep it moist and clean.
Wet the bristles of a soft-bristle toothbrush with the soapy water. Tap it on the edge of the bucket or bowl to remove excess water. Scrub the corners and crevices of the window frames with the toothbrush.
Wet a cloth under a stream of cold water. Rinse the soap from the window frames with the cloth.
Dry the water from the window sill with a dry cloth.