Rachelle Gardner has a post about creating strong characters. While she says at the end these are not rules or a checklist that agents use she has some really good points about making well rounded characters.
Some of my favorite points:
Characters need to be active. I like this because my characters tend to do a lot of thinking. Which is not bad, but they need to act on their thoughts.
A reader needs to know how a character draws conclusions. Ever read a book when a character suddenly figure something out and you don't have a clue how they jumped to that conclusion? I have. I had to go back and read the last page to see if I missed something, I hadn't. It made it hard to follow any part of the plot associated with that thought because I was vexed and suspicious.
She also said to avoid overstated emotion. Her own rule of thumb is that the protag should only cry once. My protag cries a couple times but never in a weeping, wailing, overdone way.
There are a lot of other good suggestions and I recommend giving the post a peruse.
What is your character advice? And just out of curiosity, what do you think about protags crying? Does it mean they're weak, or human?