There are a lot of ways to warm up before an intense workout.  The purpose of the warm up is to get your heart rate up and to warm up the body so you can properly stretch and prevent injury.  If you do not know what type of warm up you should perform, or you need to challenge yourself, try some of the exercises below:
Jumping Jacks
Pushup
Vertical Jump – Burpee
Running in Place
Vertical Pushup
Dive Bomber
Jumping Rope
Bounce/Hops
Squats
Side Switch
This is a brief list of what you can add to any of your warm ups.