One thing I love about being a pantser is the process of discovering who my characters are.
When I start a story, it's usually from a random scene that has popped into my head. It's almost always dialogue, which makes me feel like I'm eavesdropping on a conversation between two people who just eased into view. I sit there, quietly, and try to look like I'm minding my own business, when I'm actually minding THEIRS.
Then I go through the usual first impression stuff we all go through when we meet new people. We notice what they look like, and despite our best intentions, we make judgments based on our previous experiences. Since these are heroes and heroines, there isn't a lot to criticize at this point.
But, just as with people we encounter in real life, there's a lot we don't know about characters when we start a story. If we did know everything, the happily-ever-after would be at the beginning of the book, not the end.
I think it's fun to learn new details about the hero and heroine as I move through each chapter. When I'm writing, I'm constantly picking up on the clues they toss my direction, usually via an offhand phrase or an unexpected response to another character's words or actions.
This is when I stop to plot and ponder and decipher exactly what this information reveals about the character. I'm in awe as I learn what is important to them, and what they are going to fight for, and what they are willing to sacrifice.
The tricky part is when a character won't give up their secrets. Even worse is when they do give you juicy information and you're not sure how to interpret it, or how to weave it into the story. I won't even mention how heartbreaking it can be when they drop a bombshell in your lap, requiring you to dismantle chapters you lovingly polished before that shocking moment.
Still, I'm not sure I could write a story where I knew everything about the character ahead of time. I enjoy that slow unfolding of character traits, that leisurely method of learning what makes a particular person tick. It's a process that involves trust, and a huge amount of it. You can only expose your inner self when you believe no one will try to harm you with the information you're divulging.
It makes me happy when my characters demonstrate their willingness to put their hearts in my hands, trusting that I'll take care of their hopes and fears. It's a little frightening at the same time. But hopefully by the time they give me that responsibility, I'm so in love with them, there's no way I can say no.