NO means yes, YES means yes.

I went out to dinner with a bunch of friends, which accidentally, happened to be all guys. So of course they ended talking about this hot chick and that hot chick while I ended up sipping on soup.
One guy complained that it is hard to approach girls because he just doesn't know how to. That, and the fact that he was scared of rejection. "You just gotta do it, man," one guy replied. "I have an office colleague, who's not that good looking at all, but he just puts himself out there, and buy the end of the day he will always end up with a phone number or a business card."
Well, that is sort of true. Sometimes when a girl says no, it just means, "try harder, stupid." And if you try hard enough chances are she might give in. I know I would.
"But then," I chipped in. "You still have to know when a girl is subtly rejecting you. Sometimes she wants to say no, because she's really not interested, so you have to know when she's being subtle about it out of respect for you." The guys looked interested. "Usually," I carried on. "When you ask a girl out to dinner, and she accepts, but at the same time tries to invite other people to join you, that's most probably her way of entertaining your offer while rejecting you at the same time."
At this point my friend looked shocked, and as if a sudden revelation had fallen on to him. "Son of a bitch," he said, flabbergasted. "That happened to me so many times before! I had no idea that's what it actually means!"
You're welcome, guys. Glad to shed you some light on this matter.