from a sub's point of view
It is not a major problem to identify a strong, assertive, intelligent woman. She holds herself with poise, confidence and grace. By Her very nature She stands out in a crowd. Women like this can be found most anywhere, the hard part for a submissive is approaching these Women, without being rejected or ridiculed.
First put yourself in her mindset. She doesn't want a blubbering idiot. Nor is it an interest to Her to have to be in a particular role (the Dominant Bitch-Queen from Hell) all the time. i have found many of these Women want or enjoy an intelligent, understanding partner who is willing to put Her desires before their own. A companion She can talk to, have dinner with and when She is in the mood "play" with. In many situations the Domme/sub air is there but the cat-of-nine-tails and the flogger are put away.
So on the initial approach remember to be yourself but remember to be respectful. Try to make Her feel relaxed, a bit of humor cant hurt…if not used in excess (this may demonstrate you have some with). A small token on the initial visit is always a good gesture. This could be as simple as offering to buy a drink for Her at a bar. Or bringing flowers or candy on your first meeting alone.
One key thing i must stress is not to be overly sexual in your approach. Men and Women look at intimacy differently. Remember to take Her point of view. When offering to be of service to Her, do not even think or mention anything sexual. If it is Her desire to take the relation there fine…if not then remember each Dominant is different in their style and approach to this lifestyle.
If play should start do not insist on what kinds of play you will and wont do…rather that is topping from the bottom. Prior to play you should have already informed Her of your limits, your fears and your experiences (good and bad). From here She becomes a creative director to play within your limits while working with you to expand on them in time.
So to sum up, be yourself, make Her feel comfortable to be around you, make Her smile, treat Her like a Queen, but don't over do it. If you do, you may appear to be a mindless pathetic idiot. Remember it is Her pleasure you are seeking to achieve, if you do this She may choose to bring you into Her realm of dominance.
Finding Dominant Women is not the hard task, rather approaching on and establishing a relationship you both can live with is the hard part. Be yourself, leave you ego and expectations at the door and open you mind…you will be fine.