How are you doing it now? Do you think, the blue, the red, the green, etc? or outside, combination, skinny, etc?
Personally when I'm doing a jumper course the simpler the easier. Doing it to a song, or word association or whatever methods people would just confuse the heck out of me. There are too many things to think about on course! I just put the number to the jump. That's jump one, there's jump two, jump three, etc etc. Usually when there's a jump off (or work off in an eq/medal round) all they tell you is: jumps 3, 4, 6, 1, 9. You have to know which jump jump 3 is, right? So it's a good idea to train your brain to match numbers to the jump.
I firmly believe memorizing a course is an exercise for your brain, just like riding without stirrups is an exercise for your legs. Some people have to work harder at it then others, but the more your practice the better you get at it. Practice memorizing courses at home. When you aren't jumping give yourself "tests" on the flat (cut across here, circle here, etc etc). In highschool I was a waitress and I used to try and memorize people's orders. By the end of the summer I could do a table 10 (salad and drink orders too!) without writing anything down! (the downside is you CAN'T make a mistake!!) You WILL get better, but it will take practice!