Characters are vital to any story. They can carry even the most hackneyed plot devices and keep readers hooked through the darkest, most awful storylines. Characters can be good and noble, dark and dirty, liars, cheats, or Dudley Do-rights -- but they have to be consistent, believable, and real.
For me, character and plot are closely entwined. Characters drive my plots, and plots drive my characters. Being a plotter (not a pantser,) I do a lot of this work before I begin writing -- but writing is also an important part of developing my characters. I keep learning more about them, right up until the story is finished.
If you have anything character-related that you'd like a second opinion on (character development arcs, motivations, background, etc.) feel free to email it to unicornbellsubmissions at gmail dot com, or post it in the comments and get even more feedback. Questions, suggestions, pester me for more links, don't be shy.
Stories about how your characters surprised you or hijacked the plotline are always fun, too. Or whatever shenanigans they get up to, in your head. I have something like a green room where my characters can lounge on sofas, eat pizza and goof off. A lot of crazy stuff goes down in there. What about you?