that's one thing I am glad of, I can remember a course off the bat, sometimes 3 at a time for jumpers!
Make a song out of it, or name the jumps ex: red oxer, blue skinny, green vertical, scary flowers, 6 stride line, diagonal, etc.
In Hunters I find it simple, you can not jump any of the jumps backwards, there is always a place to go where the jump isn't backwards (If that makes any sense?)
In Jumpers, the jumps are usually numbered so that helps! And walk the course with a coach so you have a "game plan".
If you have a really hard time remembering it, wait to go you turn after a few rounds of watching other riders and repeat where they are suposed to go as you watch. Tell someone (coach, parent, friend) the course over and over and over also.
While on course, always be looking ahead to your next jump to prepare, I always look to my next jump in the air.
Good luck & have fun!