Here's another trick that works where a torque wrench either isn't available, or there's just no room to use one:
Turn the bolt until all the slack is taken out between the parts, and the bolt stops turning freely. It's pretty easy to feel when all the slack is taken up. Then turn the bolt one more flat (1/6 turn). Since the parts aren't getting any closer together, the bolt must stretch for the thread to keep turning. 1/6 of a turn puts about the right amount of stretch on the bolt, no matter what diameter bolt you're working with, and it's easy to get a good estimate by watching the hexagon head, or even marking the area beside the corner of one of the flats with a sharpie.
Jerry
