Make your beam cartwheel as much like your floor cartwheel as you can. Most gymnasts in their learing stages change the way they move through a skill when they do it on beam. I can understand the frame of mind that makes a gymnast approach their beam skills this way, but the logic fails to impress me. Why would you take a skill you do so well on a floor line and change it into an "un-familiar" skill when trying it on the beam? It seems to me that changing to an unfamiliar skill just when you need it to be your best is like putting on greased shoes to walk a tight rope.
I'll "vent" for a moment on a few "classic" changes I see being made...
Hesitation before the skill and during the first part of the skill
Using an entirely different rythm, either faster and earlier, or slower and later
Using different body positions, especially the head turning or reaching to see where you're going.
Take a moment to consider which of the other events you treat "new" skills this way. Would you really think it best to hesitate and slow down as you approach the board for vault, or as you brought your feet to the bar for a kip?. If I asked you to change the rythym of your clear hip, or a pirrouette, both of which you do very well, would you smile and say "sure, I bet that'll make it easier".
I hope you get what I mean when I say that most gymnasts run into trouble because they think balance deam is sooooo hard that they have to make their perfect skills less than perfect and harder to do when working them on the beam. Now that's the way to make a ho hum event like beam become a difficult adventure. Just remember to start your beam skills with the normal rythym you learned them with, and make no changes in body positions. After that it's a matter of aim, concentration, and finishing in good alingnment.