Trick to unions?

[mitchgo]

What do I need to look for to know I'm unscrewing a union already in the ground?

Oddly enough I say about 75% of the time I tighten the sucker at first before I realize I'm going the wrong way. Is there something I can look for on the union it self to see which way it goes.

Problem is .. there is a ton of different kind of unions and brands which are all different threads and styles ect ect..