Hunter jumps may not have numbers on them, but the courses are not as difficult to memorize as you would think. A well-designed hunter course has an easy flow to it, and once you know what the typical course design is like, you should be able to find your way around almost any hunter course just from knowing the first jump alone!
After the first jump, the course will go to either an outside line (or single oxer) or a diagonal line (or single oxer). Generally, a diagonal will follow an outside and an outside will follow a diagonal. The best part? Usually, there will only be one line of jumps to take from the proper direction after coming around the end of the ring!
One course might be inside, diagonal, outside, diagonal, outside. Another might be inside, outside, diagonal, outside, diagonal.
How should you memorize the course in the quickest, easiest way? Remember the first jump and the last jump. That's it! You should always run through the rest of the course with a ground person before you enter the ring, just to make sure that it follows the usual formula, but it's really no more complicated than that for most hunter classes. Even if the course includes a broken line or an in-and-out, it will still follow roughly the same track!
As you go around the course, make sure that you don't jump anything backwards. Check that there's a nice ground line in front of everything and you should be good to go (since hunter jumps have such large ground lines, the back of most jumps will have an almost false ground line since it is pulled out so far in front). It's very rare to have a line going from an oxer to a vertical in a regular hunter class, so if you see an oxer (likely facing the wrong way) as the first part of the line, it's most likely not the jump that you're meant to take. Keep going around the course until you've gone over that last jump that you memorized!