Disclaimer: I'm no Jackson Galaxy. But pets, both cats and dogs, communicate with their owners in their own way.
Cats are a lot about body language.
For your question I just look at the ears and the tail. When the ears go lower and/or tail starts wagging, I stop. Or when my cat moves a small distance away, sits there and stares/smiles? I stop.
I've noticed that what I interpret as a desire for petting is often some other business. Maybe the litterbox is full. Or maybe it's playtime (thinks the cat). Or something else is amiss.
It maybe sounds stupid but when I can't read my cat, I usually just ask. I say repeatedly "show me", "where", "show me", "where" etc. and slowly walk behind my cat and let it lead.
For example, if the balcony door is open and cold air is coming in (my cat doesn't like cold), my cat sometimes takes me to first to the fridge and then leads me to the balcony door. When the litterbox is full my cat takes me near it and sits there facing it, within visual/smelling range, but never very close to it. And so on, one has to connect the dots from the context, and ask the question "what is there at this location that is meaningful to the cat".
Of course sometimes I can't fix what my cat wants. Like when the Sun has moved away and the sleeping place in the chair has fallen under a shadow. So my cat tries a few times, repeating the same behaviour, but eventually gives up, either gets bored or realizes I can't or won't help.