Ah, yes. I coach cheerleading.
Two phases (from feet to hands and hands to feet) are my focus.
1st phase. The reach, 1/4 turn side, and back kick. Things to watch for:
-good reach: but that's pretty self explanatory. I would also make sure they have the feet far enough apart and the front leg is bent enough, so they're not just levering in close.
-back kick without turning out early. The back kick should be strong during the forward reach. I'm not sure if that makes sense, but I'm sure you've seen it where kids turn out from the hips early and are kicking more side. Even when that's not incredibly pronounced, it can hinder the skill (also probably isn't great for the hip joint). Make sure the 1/4 side is late.
-back kick is STRONG
-through support phase, there is a good stretch. Hands are relatively close together. Shoulder width. I don't usually force a second hand turn in but some should be natural. I just watch for turn out. If the hands are too wide, the center of gravity is lower and the skill won't accelerate as well.
-I deal with a lot of problems with the approach but depending on the skill level and where you're trying to go, sometimes you just have to cut your losses. I just make sure they are reaching and not leaping from the back foot to the front.
Because there is so much room for error just in starting the skill, I'd work on cartwheels more and make sure their arms stay by their ears (they don't drop to shoulder level). When they can do a good forward cartwheel from lunge to lunge on a line, then start cartwheel step in (after the first foot comes down, quick lever up to bring the second foot next to it). This is pretty key. Do everything on a line. If you want to mix it up you can put down some dots or stars in a line for them to use. Make sure the head is always in ("cover your ears")
Cartwheels over mats. Cartwheel step in onto a mat. When they get good, tell them to do it so fast they have to take steps backward. Arms should stay by the ears. Set up some different stuff to make it fun (cartwheel steps backward up a wedge, do it on tumble track, do a punch stretch jump out of it to touch something, do CW step in punch stretch jumps bounding backwards, have a relay race doing CW step in punch stretch jumps bounding backwards)
Good HS is also important for the support phase.
I'll start with that because I have much better luck with ROs when they can do those things well. I think it's easier for them to reference the beginning "requirements" when they aren't worried about the snap. Then they progress to the snap to two feet more easily with pretty intuitive cues.