Making Characters Flawed

Who loves a story where the main character is perfect?  They never get mad and hit something, they are always kind and loving, they have the perfect hair and smile, they are never sad, they always win.  Wouldn't that story get kind of boring?  They easily defeat the dark lord and never do anything wrong.  The end.  My point is that your story will be like this if your characters are not flawed.  Let's look at the definition of flawed according to http://dictionary.reference.com/.

1. characterized by flaws; having imperfections"
Can you think of some imperfections that a character might have?  Maybe a girl is told that she is ugly so she is very insecure about how she looks.  Or, maybe a boy gets scared easily.  Maybe a MC has anger management issues.  Another word that can be used with flawed is weaknesses.  Weaknesses are flaws.
Characters are boring if they do not have any weaknesses.  They have no depth, therefore the story that they are in has no depth.  Do you have a character who is perfect?  How can you make them imperfect?  I have to admit, before I became serious about writing, I was terrified about making anyone but the villain imperfect, to have never done anything bad.  Sure, things went wrong for them, but they had never done anything bad.  Yeah, those stories aren't great.
So, how can you make characters flawed?  Well, first, I would brainstorm a bunch of weaknesses someone could have, maybe write down some weaknesses you have.  Second, read over the outline/plot/any planning you have done.  Ask yourself what weakness would affect the story the most.  What would make the story the most unique and interesting.  For example, your story is a medieval fantasy about a duke who wants to take over the kingdom.  While developing your idea, your character is perfect, or close to it.  What would affect the story the most?  Maybe your main character has to live with the shame that the duke is his/her brother and because the brother was abusive, your character is afraid of people.  What does he have to overcome to accomplish what needs to be done in the story?  These kind of questions will help you develop your MC. 
Remember, stories should be character driven, so don't hesitate to spend some time creating them!