Wash the glass with glass cleaner and paper towels to ensure good adhesion. Allow the glass to dry.
Pull a piece of 2-inch low-tack painter's tape from the roll and cut it off with a pair of scissors. The length of the piece depends on the length of the edge you are taping off.
Fold over 1/4-inch on the long side of the tape. This gives you a handle to make removing the tape easier.
Apply the tape along the edge of the glass with the unfolded side right up against the frame.
Continue applying pieces of tape along all of the edges between the glass and the door frames.
Cut the end of the first piece of tape going in a corner at a slight angle away from the frame. Cut the other piece at an opposite angle. This ensures the two pieces only overlap in the corner.
Continue this process until all edges of the glass are protected.
Score the edges of the tape when it meets the door with a razor blade after painting is complete. This ensures none of the door's paint comes off with the tape as you remove it.