I definitely have a jaw clenching problem too. I try to consciously keep my jaw relaxed and I rub it.

When I thought I was suffering form migraines, I discovered that some people think those night guards are actually not the best thing for headaches because it allows you to bite harder than you normally would without it and that engages your temporalis muscle which can cause very bad headaches. Experts don't know what exactly causes migraines, but this is one theory. I even spoke to my neurologist about it and she shrugged and said anything is worth a shot.

Here's a link to a picture of the muscle and what it's capable of and a webpage about an alternate to the guard (I was actually thinking of buying this thingie but the spinal tap worked for me and I didn't need it anymore):

http://www.21stcenturydental.com/smith/book/2nd_sth.htm

Here's a link to a massage therapist's perception of the temporalis muscle:

http://dmmassage.com/?p=262

And then here's someone's blog about how he relaxes his jaw and what other methods he takes to avoid getting headaches from that sort of thing:

http://www.thedailyheadache.com/2008...migraines.html

Here's his treatment plan:

-Learn to relax my jaw and monitor the problematic spot on my neck in individual biofeedback sessions
-Avoid crunchy or chewy foods (for a short time)
-Cut all food into kid-sized pieces
-Learn to chew up and down rather than in a circular motion
-Continue to see my massage and physical therapists for jaw work
-Use self-massage and acupressure to further treat muscles

Here's the link he includes in his blog with self-massage tips for the face:

http://airtravel.about.com/od/travel...sageFace_2.htm