This one is so simple...  but really significant. Sometimes you have a nut and bolt that don't quite connect properly.  You feel it grab, but its too tight.. and you turn it a little more and force it.. You are crossthreading.  It can lead to major headaches on someting as simple as a spark plug. This can improve oilfield safety too. Valves and fittings for the oil field are critical points in the system that need perfect connections.  A cross thread bolt in the wrong place is dangerous.

Ok so whats the trick? How do I stop that darn cross threading..?

simple.. first,

you should buy a shiny new wrench from affordable tools in midland texas..!

if you dont already have one or even if you do.  :)

turn the bolt backwards  just a tad.  As in left to loose..

yep thats right - you will feel it seat properly, dont go too fast. 

Now by turning it back, it seated at the proper angle and meshed.. now.. You can turn turn it to the right!