You can look at this problem as a bunch of layers on top of each other. In between the layers there are barriers consisting of consent. You must get mutual consent before moving across a barrier. We normally deal with the touch barrier, but there are plenty of other barriers that interactions run up against.
Flirting can be looked at two ways. In one, you are moving specifically across the friendly - romantic barrier. This is a limited way of looking at it. How you want to see flirting is as a general way to get mutual consent to move across any barrier.
Let’s use a specific example from my life. There is this quite fetching lady at my job who I wanted to interact with. I had no surface reason to interact with her, nor am I the sort to just approach ladies that I want to interact with. But she walked by my desk many, many times a day. My eyes were unavoidably drawn to her, and sometimes they’d meet. The barest hint of a smile would cross my face. The barest hint of a smile would cross her face.
Eventually the smiles would get freer. But we’re still not speaking. If you look at the above interaction, the eye meets and slight smiles are a form of flirting. Neither one of us is sure that the other is okay with crossing the consent barrier, but the stakes are still really low. The full smile is a complete movement across the barrier, on both of our parts. Now we’re in a new interaction space.
At this point we need to actually start talking. In order to do this, one of us needs to find a way to get close to the barrier of talking without going over. For me, this usually involves little throwaway phrases in passing. She can either respond to it or not, and there’s no pressure either way. This barrier went down extremely quickly, the first thing I said to her, she jumped on and we had a short conversation.
Once you’re talking to each other, in my case it can go one of two ways, you can start shooting for friendship, or you can start looking for romantic interest. Silly young people might try to jump straight to sex at this stage. In my case, since it’s at the office, I’m looking for friendship first. Eventually she drops into one of our conversations that she’s married. Oh well.
You can subdivide friendship flirting across all kinds of barriers. Friendship is a relationship, meaning it’s got all kinds of places it can go, including the romantic direction. You can flirt with the idea of going fishing together with your friend. It’s the same as other kinds of flirting, you approach the line cautiously and make sure you’re both stepping across together. If they don’t want to do it, you back off the flirting and find another approach.
The willingness and capability to back off is what makes flirting work. You won’t step across the barrier together this time, but you have a space to retreat back into. Only silly people issue ultimatums, where if you don’t agree to step over together right now, there is no space left to retreat into. It makes a mockery of the idea of consent and is just bad business.
Forget about tips and techniques and all of that and pay attention to the actual interactions. Take baby steps in the direction you want to go and verify mutual consent when appropriate.
One thing you learn doing this is that sometimes people really hate the slow approach. Once they’ve decided they want you, they don’t want to faff about. Try to accommodate their need for velocity but don’t compromise your own needs for it.