at what point do you give someone your actual name

Trying to build myself an actual policy instead of deciding in the moment, badly, every time.

Right now what happens is this. Someone asks a friendly question, I panic slightly, I either give a straight answer because refusing feels rude or I go vague and then feel like a weirdo for the rest of the conversation. There is no consistency to it at all. I have told one person my exact job title in the first week and gone three weeks without telling another my first name.

Things I am trying to place: first name, what I do for a living, roughly where I live, my actual full name, and the name of the place I work. All of them feel harmless and all of them are obviously not.

So where do you draw yours? Is it a number of messages, a stage, an instinct? And has anyone found a way to decline one of these without the conversation going cold, because that is the part I keep failing at.