The story you’re writing may have the kind of lead character that people automatically root for. He may be a good guy doing the right thing; or a decent woman trying to sort out something that needs sorting. Heroic behaviour and overcoming adversity can bypass the whole need to tell the reader this is someone to cheer on. It’s obvious.
But they might be a little more complex than that. Maybe flawed, maybe even a bit awkward. Or they may not get to their heroic moment until much later in the story. How do you get the reader on board as quickly as possible without having to add ‘stick with it, things get good later’ at the bottom of each page?