I just read another technique somewhere. You do this to relax though, just after you lie in bed. You get into a comfortable position, and then tense and untense your body starting from your feet all the way up to your face. Focus on all the tiny parts as well and do them separately, moving up your body as you go. So for example, for your head, try to focus on tightening and untightening first your throat, then your jaw, then your lips, etc. I'm not sure how long you should hold them for, but I'd assume something between 3-6 seconds.

I haven't done this yet. I'm actually about to go try RIGHT NOW! *cross fingers*

Cheers,
Dylan