If you want to do it right, a torque wrench is nice to have. Its the one thing that I disagree with sheldon brown on, as he says you don't need one. Even an experienced mechanic can't guage torque perfectly. If nothing else, use one until you get the hang of what a newton-meter feels like (or lb-in/lb-ft if thats your thing). Learning how to properly torque a fastener will mean less chance of bolts loosening, less chance of stripping a bolt, and in the case of square taper bb's, less chance of damaging the arms and bottoming out the bolts. Since perfect accuracy isn't crucial, one of the beam torque wrenches will work fine. I like craftsman:

here.
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