Well, I'll say it again, Redpaw and Crestlen (the main characters from my current story) were pretty flat. And it took me a bit to see it. Before I continue, though, I should explain what I mean by flat. Flat characters are one-dimensional, they don't change or do anything besides the one thing they're meant to do. A storekeeper who the main characters buy stuff from several times would probably be a flat character. He has character, but it doesn't change, and you don't see a lot of it. Round characters, the opposite, are characters that have depth, and change. You see into their minds, how they react etc. And neither Redpaw or Crestlen were doing that for me.
So now, I'm doing everything in my power to fix it. Step 1 was coming up with I call "descriptory word runs." By which I mean, "A long string of unconnected which help define and describe the character and essence of a character". So I did that. Step 2, something I haven't done before, was to create a backstory. For many of my earlier writing attempts a backstory wasn't necessary, since I started off my characters quite young, in other words, they hadn't had much time to have a backstory. And what backstory they needed I created as I went along. For Freeborn and Freegiven I hadn't made backstories, but they came out anyways as I wrote (which I'm really glad happened). At one point I even made references to something bad happening in the past between two characters, but I personally had no idea what it was. Not until later did it actually come out. (See? Writers don't always know every last detail of what's going on! :P ) Anyways, for Feather and Fang, Redpaw and Crestlen kinda need backstories. For one, they're older than most other characters I've written, so much more has gone on before the story opens. And for another, they are very good at what they do. So there has to be an explanation of how they got that good.