The title of this is actually misleading. You can't really fit flirting in a shell. Flirting is pretty hard to do if you're not used to it.
I used to be so mechanical and methodical about it. Then I somehow realized that it's impossible. It has to be something you feel. If that makes sense.
If you haven't then I suggest you take improvisational classes. It will dramatically improve your flirting skills. Flirting is improv. It's on the spot. You don't think about it. You just do it.
A lot of you are natural born flirters. You flirt with your friends all the time. You rip on each other, joke about everything, and act like goofs. In fact, I'm sure when you ask your friends about your woman problems, they tell you that if you be yourself, she would definitely like you.
Yet its so hard to be your natural funny self when your so nervous and in your head instead of in the moment.
Now this is really vague but flirting with a woman is pretty much just having fun with her. So.....have fun with her when you hang out with her.
Everyone always says this when they talk about flirting, but it really is true. Flirt=Tease. Both of you should rip on each other. If any of you had little brothers or sisters and you used to pick on them in a fun way, bring back elements of that. Like getting her all hyped about something your gonna give her and then not letting her have it yet. Real simple stuff.
Another thing is that flirting is not a stage you go through. It can happen anytime. Just like conversation it is dynamic and the more in the moment you are, the better.
This wasn't meant to be the end all in flirting tips but just my two cents. Hopefully that helped.