Are you talking about 120volts? If so get a plug in electrical tester and check the recepticle. If it wired correctly a polarized plug will have the correct polarity. If the plug is not polarized it doesn't matter.
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I love the little Van Den Hul unit. Cheap, easy and safe. What's not to like. I have 2-3 multi-meters, but I always feel a little nervous using them in new installations.
FIRST, THOUGH, start with a simple Rat Shack Polarity tester. Make sure you actually HAVE pos,neg, and ground. If not, you've got to fix that first.
If you've had your sockets wired by, checked by or approved by a qualified person or are now ABSOLUTELY SURE they're wired properly, then have at it with the multi-meter.
I wouldn't want to grab or connect (me) to a ground wire or other socket that is accidentally wired incorrectly. It is potentially dangerous,if the socket isn't wired properly in the first place, and then, even if you don't get "surprised", your VOM won't tell you anything helpful for tweaking purposes. Get the mechanics right first, then start poking.
DISCLAIMER: After reading the above references, I believe these articles are clearer than my explanation and I'm no electrician, but I've done this for years, since "Auntie Enid" mentioned it, even on my HT system.