IMO, flirting styles vary depending on the situation.
If a guy is flirting in a bar in front of his friends, he'll be a little more aggressive as he's trying to impress both the girl and his buddies. The booze might also make an impression.
If he's at work, he can show interest and flirt a little but he has to be careful as to what he does in front of his coworkers and his boss. If he goes to her work, hitting on her will be counterproductive if he gets her fired :) Also, there's a difference if they meet for the first time at work, or if one is a regular customer in the other's workplace (ie - bank teller, waiter, etc.)
If you sets up a meet-cute (http://en.wikipedia.org/wiki/Meet_cute
) the flirting could even go badly and still work out.
I think that once you know how/when you want them to meet, you'll narrow down what kind of flirting you need.
Good luck. Hope this helped.
And then it all changes again if he's alone and she's with her friends.