OKCupid is good for finding poly people in your area, for sure, although it can get a little frustrating sometimes, with the drive-bys ("Yes, of course I'm poly - can we screw now?")
Again, I am in a V right now so anybody with any potential interest in getting to know me, even as friends, knows that I am non-monogamous. I usually try to find some natural way of bringing it up in conversation, rather than making a "big thing" out of it.
I tend to go very slowly when getting to know people - I would like to see if they can be friends before I think of them in a romantic way, because I find it builds a foundation for any relationship and maybe show up some "red flags" before anybody gets "in too deep".
The best way, though, in my opinion, is to mix socially with other poly folk. Get to know them as people, rather than looking at them as prospective dates. If there is a local poly group to you, then consider going to one of their get-togethers.
"Listen, or your tongue will make you deaf." - Native American Proverb