Question: I'm writing a novel in third person limited on an online site, and while everyone loves the protagonist with all his quirks and awkward nature, I'm struggling to characterize the other main character. The readers tell me they feel as though they "don't know him" although I've mentioned his back story and shown scenes with him interacting with the protagonist. I've tried filling out character questionnaires but I don't understand how to include those facts into the story. How do I flesh out this main character?
Of course, I haven't read your piece, but here are some general thoughts...
1. Be wary of taking criticism to heart. On an online site, you may not be getting expert advice. As Neil Gaiman says, readers can tell you if a story is not working for them, but they can't tell you how to fix it. Also, some people just like to push your buttons. Focus on making the story express your vision.
2. Characterization is not about how many facts about the character you include. The details are important for you to build up an understanding or image of the character in your own mind, so you get a feel for how the character will behave. But the key is letting the character speak and act in his/her unique way. The only traits you need to include in the story are those that are truly telling and significant; the rest stay in your notes. Including too many details can make a character and the writing seem dull. The writer can end up looking like she's trying too hard.
3. Something to bear in mind is that great characters are...
Authentic - they feel like people the you would encounter in real life.
Unique - they have a few traits that distinguish them from everyone else.
Consistent - in they are always themselves and their traits don't randomly come and go.
Surprising - they can defy expectations or have contradictory aspects to their personality.
Notice that these qualities contradict each other? People are like that. That's what makes them interesting.
4. I take it your story is not finished yet, and therefore it may be okay for the readers to not have all their questions answered already. By the end of the story, they may come to know the character better. Don't feel you have to tip your hand early. Sometimes it's better to have the character behave in mysterious ways and make the reader wait to find out why.