Make a cheer. The easiest way to make a dance routine of your own is to learn the cheer first.
Count the syllables. If you count how many beats in a line, you can easily choose the moves you can make in time.
"We're the best in the west!" would be four seconds long
Listen to the music you are using. Listen, count the beats, and familiarize yourself with it so you know exactly when to do the moves. Try to know every beat, rhythm, and sound of the music so that you will feel comfortable doing your moves - comfort will bring confidence, and confidence means great work!
Merge. Take the syllables and beats to the song, and sing along!
Random moves. As soon as you got the above steps down, start to dance around a bit to get used to the rhythm and beat of the song.
Use your mind. Hopefully, the right dance will eventually pop into your head. When it does, quickly write it down, and try to remember as much as possible. Practice and play around with it until you finally come up with the final moves, and then you can teach your crew your dance.