Good points above. One scientific fact (if this helps): women are horniest during ovulation (right after their menstrual period). There's an obvious genetic reason for that. Women are much more likely to go out and hook up when they are ovulating. So, don't bother trying to determine if someone you're talking to is ovulating...if she's out in a bar talking to you, assume that she is.
Don't misread the scientific fact however...I wouldn't say this means that you only try to pick up women who are ovulating (even if you could determine that). I'd say it sounds like an awefully good excuse to have about 4-5 girlfriends...if you pick one's with the right schedule, you could always have one who is ovulating.
(This is a joke...but the thought is definitely appealing isn't it?)Gruuve