So I don't know if this is already a known principle but here's what I've observed about a male's seductiveness and laughter. Don't do it.

I can theorize as to why, but I have observed (within me and other women) that a man who is funny but does not laugh with you, or always keeps a poker face, is extremely sexy. I don't know if it's a nervous need for approval that makes a girl want you to like her if you're not laughing your ass off around her, or if it just shows that you are in control of your emotions and the situation, but I think there's something to it.

So next time you're out chatting up girls, stay in control and make them laugh while appearing to be unamused. Obviously, don't border onto cranky but a little cocky restraint can be hot :)