[knobtwiddler]

The time to really observe this rule is when working with materials that easily gall when cross-threaded. A good example is stainless screws going into stainless threads. Always use some grease, always observe the reverve-twist-until-it-clicks method - and immediately go backwards if you feel unexpected resistance when screwing in. If a screw is in any way suspect, bin it without hesitation.

Edit - another tip: if you're using detachable driver bits and the screws aren't large, then take the handle off the driver bit and hold it in your fingers. This way you won't accidentally cross-thread it due to the extra torque afforded by the handle. Put all the screws partially in with the bit alone, and do the final tightening with the handle attached.