Are you meaning jumping courses? (You said showing but you are in the jumping thread?) what discipline...
For jumping I say the course out loud - usually saying somethign like red double turn right green jump 4 stride green oxer turn left etc and just keep repeating it so when I do the course it all makes sense
For dressage - I do the whole thing on a piece of paper and then make myself read it at least once efore I go to bed and once when I wake up ... you constantly find me drawing the course in the air with my finger as well
Showing workouts - have a set one I use if I have to else the judge tell ya (But Im not a showy)
The best way is to look at the arena and have someone tell you th course. EX: White verticle with pink flowers to the outside green 6 stride, to the gray diagonal 7 stride, to the white judges line in 4. Its best to name the jumps and if it is a rollback, line, or bending line you can remember 2 jumps under 1 name :] It makes it simpler. Then go over it in your head and repeat the course to a friend who also knows it
What helps is to walk it, with a trainer. Then stand in the arena and look around and go thorough your course just turning and looking at how it goes. Then say it to someone and go over it in your head. Then watch a couple of runs to see how it is riding. That's what my trainer always has us do