What to do when my computer freezes?

Ok, I want to know what I should do when my laptop freezes and the mouse doesn't respond, and hitting the ctr+alt+del keys doesn't respond either. I know that I can turn off my laptop by holding down the power on until it turns off. I know this can damage the laptop because I have already needed to replace my hard drive once because of that but I really don't know what else to do if ctrl+alt+del doesn't respond. So, what should I do when my computer freezes and nothing is responding? What should I do to not cause damage?