Use free writing to build characters.Make a list of emotions. Each day free write for 15 minutes -- that is write without pausing, push the ideas out -- about what your character thinks about the emotion, what emotions it elicits for him, experiences he's had with it in himself and in others. Anything and everything that flows out nonstop for 15 minutes.
There are several lists of emotions on the internet. The one here is from Basic emotions - list of emotions.
Wikipedia also has a list of Emotions.
And at Burning Void: Passion (though some seem more akin to characteristics).
(From an idea posted by Sesselja on the National Novel Writing Month (NaNoWriMo) forums.
love
compassion
sentimentality
lust
passion
infatuation
longing
joy
satisfaction
ecstasy
enthusiasm
zeal
thrill
contentment
pleasure
pride
triumph
optimism
rapture
relief
amazement
aggravation
frustration
anger
hostility
hate
scorn
vengefulness
resentment
disgust
jealousy
torment
suffering
depression
sadness
grief
disappointment
guilt
shame
remorse
alienation
loneliness
insecurity
embarrassment
humiliation
insult
pity
sympathy
shock
fear
panic
anxiety
dread
Only three months away from this year's list but I just came across this: Merriam-Webster OnLine posted a list of 

Write 35 (or more!) *ways* for a character to murder another. Again, push it even if they start sounding wacky. Try doing one or more for each letter of the alphabet. It might knock some more ideas loose!


Write 35 motives for why a character would want to murder another. Push it even if they start sounding wacky.
Choose a hero and a villain. Set the timer for 10-15 minutes and write their latest encounter.
Write a story that contains one of these sentences.
I'm going to collect some "writer's block" tips. I don't like the term writer's block. It sounds like a disease that will stay with you until find a cure. Which only turns it into something worse than it is.