What to do about Bullies?

I am reading a book called Nineteen Minutes by Jodi Picoult.  It is about a school shooting.  I am only about half way through the novel, but it has really got my mind churning about what is the right or wrong way to deal with a bully.  You see, the boy in the story was teased and abused relentlessly by his classmates and even his older brother since the first day of kindergarten.  His parents were blissfully unaware and totally shocked when one day he shot 10 people at school.  One point of the novel thus far is that the shooter is someone's child just like the children who were shot.  He has a mother who nursed him when he was sick and washed and laid out his clothes for school just like the other kids.    None of us what to be the parent of the bully or the one getting picked on.  So how do we help our kids. 
Well let me start off by saying that I am no expert!  I really just want to open the discussion to the viewing audience to get some feedback that may help all of us.  I have a little personal experience with bullying.  In fifth grade I was bullied by a boy in my class.  He would trip me in the hall, pull my chair out from under me, and slam my head down into my desk.  My friends told me to tell the teacher, but I was so scared of this boy.  Finally one day he kicked me so hard in the shin that I bled.  My friends demanded that I tell the teacher.  So I did.  He never really bugged me after that.  I don't know what punishment he received but it must have worked. 
I also experienced a lot of intimidation from an entire group of girls that ran around together in middle school.  They would make up stories about things that I had done to them that required them to get revenge on me.  They also would threaten to hit me in gym class where it would look more like an accident.  They never actually ever hit me, but one of them did attack my friend while we were in the locker room.  My friend had walked in a few seconds ahead of me and the girl that was waiting inside jumped on her and started punching her in the head.   I didn't know what to do. I was completely in shock.  But when the bully saw that I was standing there, she stopped and left the room.  I don't think my friend and I told anyone about it.  Telling on bullies can sometimes lead to more violence because they see you as a rat. 
My youngest brother was often bullied and it infuriated my other brother and I.  We often weren't there to witness it or to help him.  I do remember that we walked through the school with him one day after he had been slammed into a locker and had his backpack thrown down the hall.  We wanted to give him safety in numbers so that no one else would mess with him.
When my husband was young, if someone bullied him, his parents told him to ignore it the first time, but if the kid kept messing with him, then he should defend himself, even if it meant getting into a fist fight.

So what have these experiences taught me?  Well I am not in favor of fighting violence with violence, but I think kids should be allowed to defend themselves, just like adults are allowed to do.  I also think there is safety in numbers.   Bullies are less likely to pick on a kid if he is with someone else.  Now I know that there are kids who don't really have any friends.  But here is where we can teach our kids to help.  I want to teach my kids to stand up for the little guy.  I want my kids to tell the bully to stop if they see him/her picking on someone.  And I want someone else to do the same for my kids. 
I think one of the best deterrent of bullying is when the bystander speaks up.  Kids and parents, don't sit on the sidelines and say nothing!  Get involved.  You don't have to throw a punch but make your presence known and let your voice be heard. 
I would appreciate any thoughts on this subject!