This is by onyxofborg on Tumblr, or onyxofborg.tumblr.com/post/156543098469/how-to-make-people-care-about-your-characters
Make sure to check them out, because they're really awesome!
-Give them interesting and complex relationships, not just "I hate your guts!" for no reason
-Show us how they feel about things. Use vivid words and don't forget to describe physical symptoms of their emotions: sweaty palms, stomach roiling with nausea, that sort of thing
-Don't harp on the same emotion for 100 pages. Give us a little variety and contrast emotional states with each other
-Even if they're the villain, show us why they think they're right. And if they're the good guy, make them wrong sometimes. No one cares about a person who's perfect all the time.