Teaching a 4-year-old to write the alphabet can be a fun and rewarding experience. Some tips to help them learn include providing them with plenty of practice writing with pencils, crayons, and markers, as well as providing them with a comfortable place to sit and write. Additionally, you may want to consider providing them with visual aids, such as alphabet charts or flashcards, to help them remember the letters. Finally, it is important to be patient and encouraging, and to provide plenty of positive reinforcement.