If you have a door in your house with glass in it you will need to prepare differently to paint a glazed door. Preparation for this project is the key for a clean, crisp, professional look.
Before you begin, make sure the door is clean of dirt, wax or anything that paint cannot adhere to. You will need to mask the glass in the window to prevent the paint from getting on the glass. To do this, unroll the tape as you press it onto the glass and use the box knife or putty knife to cut it off straight on the edges. Make sure all inside edges of the glass are covered.
When dipping your brush into the paint, wipe a bit off on the edge of the can or roller pan so you are working with a brush that is not dripping wet. Try to use the driest brush possible when painting near the tape and paint as if the tape weren't there. A build up of paint on the edge of the tape may cause paint to seep underneath and stick to your glass. It will also create a ragged edge when you remove the tape.
After letting the paint dry for no more than an hour, remove the tape slowly and at an angle. If there is any paint on the glass now is the time to remove it with a rag or scrape it gently with a box knife being careful to not scratch the glass.