After you have been doing it a while you will be able to do most fasteners by feel and not do any damage. Newbies should learn what certain torques feel like. Multiple bolts on things like manifolds or heads should always have their torque measured but we dont have that sort of thing on bicycles. Lubrication is important. A dry fastener as it nears final torque can partially seize and become overtorqued. Stainless, or steel into aluminum should have some anti seize applied so they dont seize or oxidize over time.

-SP