Flirting is a natural first step in human reproductive strategy. It is composed of several back and forth fitness tests that act as a filter for quality partners.

I know it doesn't seem like this but it really is.

First you need to be accurately aware of what your best physical features are, yes I know it sounds petty but humans first check of 'hey do I want to bang them?' is always a physical once-over.

If you have full lips, smile and talk in animate ways, giving them a chance to focus on your face.

If you have gorgeous hair, it helps to touch or play with it a little, show off your silky locks.

If you have nice forearms (yes some people are way into that) then wear short sleeved shirts and occasionally touch (or better yet, get them to touch) your arm, drawing their attention to it.

Now for the talking:

Ignore cheesy pickup lines unless everyone is already drunk and/or friendly, you want to be sincerely interested in hearing about their life. This is probably your most potent flirt: legit being interested in them as a person.

It's sad that this has to come after physical check IRL but you can sometimes bypass that online.

Don't be eager to share aggrandizing anecdotes about yourself, this is almost always a turn off. On the other hand, if you can get a wingman/woman to occasionally drop a few tasteful mentions of cool things you've done, that can work really well.

Compliment them on things that they have put effort into, and contrary to popular belief that doesn't always mean her appearance. Naturally hot girls will have been told on the daily since toddlerhood that they are pretty so they are tired of it but instead may respond well to compliments on her choice of dress, as this something they choose and likely have spent a good part of their life learning how to maximize the effects of their outfits. This works ESPECIALLY on 9s and 10s but you need to be up on fashion for it to impact the best.

Naturally hot guys on the other hand aren't so guaranteed, some of them have never been made to feel hot so if this is your angle then you can try complimenting their looks and see where it goes, but again the real hook is complimenting something they obviously put effort into.

Humor: If you have a good sense of humor, it works like the top mentioned 'physical bests' because humor, I joke you not, is a great reproductive fitness test as it indicates a clever mind. If someone is laughing sincerely with you in a flirty situation, there is a good chance they want to bang your stuffing out.

People who laugh easily and deeply, over things that others also fund funny, come off as relaxed and interesting.

Not all humor works of course, but this is part of the fitness tests. If someone you are on a date with starts cracking cruel or bigoted jokes, you know where their mind is. Also: don't do these things yourself, but that goes without saying.

Next, if you are getting positive signs: Smiles while sideways glancing, lip displays (like how women look in lipstick ads), 'pigeon toe-ing' (google it, it's hard to explain, also it's mostly a woman's sign. Men's version of pigeon toe is them leaning forward in the chair, interested) then it is time to take a big risk: Lightly touching their arm or shoulder. Also keep in mind YOU should be giving off these kind of things too, sideways glances at their hair or outfit (avoid constant boobvision, they know you're staring), cute little fluff statements that almost but not quite approach being cheesy pickup lines

This is the real test, you will see how your touch causes them to react. If there is EVEN the SLIGHTEST bit of coldness then back down and go back to conversation. You can almost feel in the texture of their skin whether or not they want you to touch them. If you live with a cat or a dog you may be familiar how they can make their skin kind of rough in the places they want you to scritch, but kind of slip out from under your hand when they don't, that's the same with humans just a bit harder to notice.

If the genuine interest, flirty looks, and positive touch response are all there, congrats you have successfully flirted!