What are you doing for first dates? There was a female that posted a few months ago that was terrible at first dates too and I think some of the same advice applies. Besides meetups and meeting people thru a common activity what about dates that include an activity so it isn't just intense conversation? It might be interesting to read the female perpective of being nervous on a first date.
Here was the earlier post
http://www.dcurbanmom.com/jforum/posts/list/15/603011.page
The other thing is realizing if someone is attracted to the hyper talkative salesman version of you actually wouldn't be a good match because that isn't really who you are. The person that you feel that spark will want to know that you are interested in knowing more about her and it is more than just her looks. If you spend all your time selling yourself, it will make you seem self-centered. One of the things about my now DH when we were dating that definitely tipped him over to boyfriend material is that he listened and would remember the little things for thoughtful dating gestures.