I don't talk about my kid to new girls. Hold off on it as much as possible. Your goal is to get to know about them, let them beg for info about you. The whole be mysterious bit.
If they ask I tell. I tell them my schedule, I never badmouth her mother. Usually once they get to know me and they see how good of a father I am, they love it (sometimes a little too much, like wow, what a good dad, he'd be a good dad for my kids).
If they are younger and don't have kids, expect that to be a turn off. Which is why you don't tell em. Of course I won't consider a younger chic for a LTR anyway so it's none of their business. I was seeing this 21 year old for about 2 months before her dumb ass figured out I had a kid. I just never mentioned it. She was too dumb to keep but she still keeps calling. It never impacted her life so she didn't care. WHen I have my kid I don't bring girls around and I don't talk to them much during those weeks/weekends.
Older women with kids, will try to connect to you via your kids. They know your kids are your heart so they will try to get close to your kids to get close to you. My current girl has tried to meet my daughter, buy her a birthday present, and asks about her constantly.
Hope some of this helps. Good luck.