the way u keep your arms straight and exact is that u have lock your arms as if you were a robot then you still move your arm like the robot does

uhhhhhhhhh

NOTHING

you stay tight

you lock your arms SO tight that you are shaking,thats what i dooo!!!!!!!!!!!

A lot of cheerleading motions do not feel natural until you've been doing them for a while. Often, motion positions can feel correct, but aren't. When hitting any motion, you want there to be a straight line from the middle of the knuckle on the back of your hand to your shoulder (or elbow depending on whether or not the motion half or fully extended).
The best way to train your arms is to practice in front of a mirror (or large glass doors and window at your school or gym). This way you can see the difference as it happens and eventually what is actually the correct position will also feel like the correct position and become a more natural movement.

All you pretty much have to do is stayy really tightt! And control ur motions you have to tell your arms where to go then your motions will be flawless:)