One of the most important things to remember when creating a fictional character is to show, not tell, the reader how a character reacts in certain situations. You can tell your reader the character was sad after her cat died, but if you create dialogue or a setting to go along with the character's emotions, it is much more effective. I have this character, Sam, in my second book that I'm trying to portray as an egotistical jerk. This is just a cover though because he's really a sensitive guy dealing with some issues. I realized during my review that I wasn't quite pulling off his split personality so I added some more dialogue during his first appearance. Kody wasn't in the least bit impressed with him, which was my goal.
On a related note, I was looking through my son's grammer book and was pleasantly surprised to see that it included a small section on this exact topic. I think it is awesome that this is being taught at such an early age.