This article is also helpful
http://www.aafp.org/afp/20010201/467.pdf
I've had good luck using trigger point massage. You can do this
yourself at home and even if doesn't work for you, all you've lost is
couple of minutes of your time.
Probe around with your thumb and find the most tender (painful) spot.
This spot will often feel like a bit of a hard lump. Push hard on this
with your thumb for 20-30 seconds a couple of times. (This will be
painful but push as hard as you can bear it, within reason - remember
it's only a few seconds). You may need to repeat this once or twice
playing with the angle, particularly when you're just learning to do
this. But if it works for you, you should notice an immediate
signficant improvement that lasts for a day or two.
Rolling the bottom of the foot over a can, thick dowell, rolling pin,
etc. can be helpful as well.
Note that while massage and rolling my temporarily relieve the
symptoms, you still have to do stretches, exercises, etc. (described
in the article linked to above as well as in any number of other
articles you can google up) if you want to address the underlying
problems and stop it from happening again.
