I like the look, the laugh, and then the touch. They might seem a little common if they are separate, but together they are a lethal weapon. The look is that deep drawn in look into your eyes that's just asking for something. The laugh is that signal that she knows your funny. And the touch on the knee, shoulder, thigh, or arm is just the icing on the cake that lets me know what's up :)
For me, personally I think it would be a flirty smile and, like, you taking your hand and touching mine with it, like in that order , not necessarily right after each other but with a little time in between, kinda subtle, but still enough for me to accept it, smile and plan to flirt back, just as much, and then keep it going.
The finger tips making contact with the hands or arm during a conversation on the first date. I also always liked the girl constantly curling her hair with her finger while giving you the look like she wants to jump all over you right there in front of everyone.
Men love it when they tell a joke and the girl looks all coy and laughs sweetly. But the important note here is she stares him straight in the eye and looks like she wants to look at him to draw him in. It works try it =)