I use an inexpensive click-style torque wrench. Since I've only installed one cassette, one BB, and two cranks, I don't have any feel for how tight they should be. I can tell you this, there is NO WAY I would have tightened these fasteners enough without this wrench. For me, the crank is particularly deceptive because the resistance increases much slower as it creeps up the taper in contrast to when you're just cranking a head-bolt into an engine.

I feel fine tightening any other fastener on the bike by hand but those three are pretty important and I want to make sure I get them right.