My experience: most women really don't like it if you ask first...they'd prefer you just to do it. And if you ask, you absolutely shouldn't phrase it as though you're asking for permission. My current strategy is to wait until the third date and then just go for it, regardless of signals. I figure that if someone goes out with me 3 times, then they're more than likely attracted to me and wanting a kiss. At the same time, I try to move in somewhat slowly to give them a chance to turn their head or back off if they're not interested, and I keep it short and sweet.
For me, the much harder thing is finding the right setting. Typically my dates end at our cars in a parking lot, which isn't exactly the most romantic setting, and may have a few on-lookers in the area (privacy is important for a first kiss).