I found this technique in "Almost
Vegetarian" by Diana Shaw: wrap the
block of tofu in a few paper towels,
put it in a shallow dish with something
heavy on top (a brick is perfect),
and leave it for a few hours. It makes
a firmer, more meaty texture, better
for stir-fries.
After I've pressed it, I marinate
it. For stir-fries, I like to use
either hoisin sauce or chili paste
with garlic, and then add it toward
the end of cooking. I've also used
a really garlicky Italian dressing
and used it in a pasta sauce.