Margaret Thatcher once said "Being powerful is like being a lady. If you have to tell people you are, you aren't.”

I would suggest to spot a Dominant you must look for leadership qualities. When the crowd gathers he will be the quiet one at the back, like the lion watching, studying, planning. Then once he knows what he needs to, he will either slowly move to the fore or pounce suddenly and establish himself as the leader of the pack.

Alternatively, he's the one with a crop in his hand