Step 1: Act
This is as simple as it sounds.  Don't just sit there and ignore what you see and hear going on around you-do something.  Educate yourself on what you don't know about or are afraid of, and spread that knowledge to others.  If you do nothing, it looks to others as if you are accepting the discrimination and prejudice around you.  Stand up for people who are being discriminated against.  Join a group that brings heterosexual and homosexuals together, or invite a gay friend to your home for dinner.  Simply acting against homophobia is a major step in breaking it down.

Step 2: Speak Up
You have the right to free speech, and homophobia should be criticized.  When you hear people talk about homosexuality in negative ways, say something.  Tell your friends you find it offensive when they use the word 'gay' in a negative way, as in to mean stupid.  When you see homosexual stereotypes in the media, point them out and comment on them to your friends.

Step 3: Unite
Chances are you are not the only person you know who feels that homophobia should be stopped.  Share how you feel with your friends. Maybe start a gay-straight alliance at your school.  Gather ideas from everyone you know that feels the same way you do.  Get people involved.  There is power in numbers, and you'll feel that once you see how many people want to act against homophobia with you.

Step 4: Talk to Leaders
Talk to your teachers, politicians, guidance counselors, coaches, and any other influential community member that you admire to take a stand.  Ask them to promote the respect and fair treatment of everyone.  If people see that important members of the community whom they are familiar with don't tolerate homophobia, there's a good chance that they'll get involved too.

Step 5: Dig Deeper
Look at your own daily behaviors and activities.  What prejudices and discriminations do you have?  Almost everyone has some, whether they are aware of it or not, and sometimes they are not meant in a mean way.  By looking at yourself, you can become aware of your prejudices and break them down. You can notice if other people do the same thing you do and you can speak to them as well.  Read about civil rights, equality, and gay rights.  The more you know the better resource you can become and the better you can fight homophobia.