2. Make some holes short for hole-in-1 potential and others longer (more distance between the tee and the hole) that are more challenging.
3. Use whatever you have - plants, trees, rocks - as obstructions you must go around or over to keep the course interesting and challenging.
4. Create some risk and reward options on the course where you can risk hitting over hazards to get a low score or play it safe and go around.
5. Most importantly - be creative and have fun with the design!