How do YOU get to know your character/s?

This is something I’ve seen quite often in writing: get to know your characters. I’ve seen it. I think I understand it, more or less. Get to know them as people: what is their goal? What drives them? What are their dislikes? What do they like? What are they afraid of? Etc.

What I’m trying to get at is you, as a writer, what do you do to get to know your characters?

I’m asking because I feel like my characters are just ideas. I have ideas of them, but they don’t feel like real people yet. They have potential to be real, but I just… don’t know.