It's not like Doms are out and about prowling clubs and back alleys, hunting for some vulnerable vanilla who doesn't know they're submissive yet, or anything like that.
How can you tell? Easy...

Person 1: Are you kinky?

Person 2: No, go away you wierdo

Or

Person 2: Why yes, I am. Are you?
LMAO, *snort*, ROTFL, *wipes tear from eyes* I'll have you know I think I've scared the neighbors laughing so hard at 7:45 in the morning, oh, I love this place...

Seriously, though, I don't know what subbmisivebeauty's situation is, but I assumed that she wasn't lucky enough to be in a BDSM club. I've never had the privilege, either, so I know what it's like to try to "sniff out" what you're looking for out of the general population. Fetish, I can't tell you how many times I've gotten response 1) and then tried to play it off as a joke after...*shudders*