Warm up exercises

Can anyone tell me of some good voice warm up exercises to help improve your voice from cracking when you sing long notes? Or other warm up exercises in general

You can get some good sheet music of voice warm ups like the Tumba Songs, or scales.
Pulsing your voice is also a very good thing to do before you sing, and you can try it on different vowels like "eeeee eeee eeeee eeee" oh "Ohhh Ohhh " sort of thing.
Also stretching before singing is good, do tongue rolls from your 5th lowest note to your 5th highest, and sirens, and lip buzzes. You can do slurs between intervals, and eventually warm up to use your full range.
um breathing warm ups are good too, but make sure you do a cool down too, when your done singing