Flirting is all about observation and escalation. Flirting is a game of fun, it is not seduction. You do it to entertain and entice, not to get your end away.
You start with a comment, or joke, or double entendre. If your flirtee responds in kind then you progress and maybe escalate a little with another comment or joke or double entendre. What's most important, though is the observation. If your flirtee backs down then you fucking back down too. If your flirtee misses the cue then you back down. If you're not sure, you back down.
This isn't really answerable in a forum discussion, as it all varies too much depending on circumstance.
I guess the basic idea is to make someone feel good and wanted without going overboard and coming across as any sort of creepy. This is a fairly fine line, though, and where it is fluctuates wildly depending on the person, situation and expectations of the moment. You're also juggling body language and tone in addition to your words, so really anything can be made flirty, or go overboard, all depending on recipient/mood, delivery and circumstance/timing.
The first thing I'd probably start thinking about is how to identify the times and individuals where any flirting will be welcomed, which is also going to vary quite a lot. Dates are a pretty safe place to start, for obvious reasons.
The other people in the thread provided some solid advice that included some loose examples. It's a tough thing to go into detail on without writing a book half full of caveats though. I don't want to try recommending a method or anything, because there kinda is no method to it. That I can think of anyway, that will be any sort of consistent.
For a while my go-to move after leaving a restaurant with a date was to say something to make us both laugh, and then put an arm around them and squeeze a bit in a friendly way.
If they lean into it, keep the arm there, physical contact makes it much easier to flirt.
If they don't lean into it, just let go and drop it for now. It's easy enough to brush off as a friendly gesture.
I also found that it's generally very sexy to actively make it easy for the other to say no. The easier they feel it is to just shut things down, the easier it is for them to keep exploring where things might go.
i guess people have distorted ideas about flirting. here's how i see it:
be aware of your goals
be honest to yourself (what do you really want)
communicate clearly. be aware of what you want and make no mystery out of it in front of the other person. if you hold back, you're blocking yourself, and that can't be good.
don't be an asshole. that's difficult in today's society where everything seems to be about exploitation and profit optimization, but there used to be a world long ago that was non-exploitative, consensus-oriented. try to feel that vibe
that should be it. if you're not an asshole, nothing bad should happen to you. however, that is practically not the case today. whatever wrong twist "feminism" took in recent years to convince society that "all men are assholes" is splitting society apart. it's provocing a civil war. society must find its senses and reject the forceful-splitting-between-women-and-men of society. in a time where even a glance is "sexual harassment" and women project their mental health issues on men and call it all their fault, is a world that is no longer honest and does therefore IMHO no longer deserve to exist.
There is no real strattegy when flirting. It's all vibes based and based on the person you try. Some might love a joke you make while others might thing it's offensive.
The only pointers I can give are: be chill, funny and nice to be around with. Learn how read the room and how zo banter. Also if you are strughling to talk to people you find attractive: ask genuine open queshions. People love talking about themselves to people that are interested in them.
I don't endorse much of anything in The Game by Neil Strauss, but for the discerning and critically-thinking mind it can provide some useful advice for flirting unawkwardly.
Started? I think the culture was already there and well established. The book just shone light on its existence to the mainstream, and yeah, probably accelerated its growth.
Edit: the irony being it was, kind of, trying to help involuntarily celibate men to figure out ways to be less celibate through seduction (vice even less moral, and more illegal, means).
Edit edit: a far, far worse book is The Professional Bachelor by Brett Tate. Anyone who ever wants to taste their own vomit should give it a glance.