This lesson is short but very important.
Your main character’s goal must be admirable or her journey will appear selfish.
Think about it. If your main character’s goal is to be Homecoming Queen, it’s hard for readers not to think she’s a little shallow and self-centered. But if her goal is to help her best friend be Homecoming Queen, it turns her into a nice person who really cares for her friend.
This goes well with Blake Snyder’s advice on making sympathetic characters. He said the character should Save the Cat, not Save Herself!