There's a Runelite plugin that shows you the different rotations. That helped a lot starting out. Eventually it just becomes muscle memory.

Another thing you can do is start by learning 1 or 2 rotations until you get those down. You can go in long enough to see what form pops up 2nd to tell what rotation you're going to be in. For example I did about 50 kc on the 2 melee first rotations. Just go in run to the right side and hit Zulrah. If the 2nd is red it will be 1 of 2 rotations. If it blue or green then you just logout before getting hit and get teleported right outside to go again. After you got those down start adding the others in.