Have the courage to stand up and do something.
Stand up in the crowd that decided to sit down because no one else chose to stand up. Chances are, once you do stand, at least one other person will follow. Muster up the courage so that you can give someone else the courage to do what you have done. Inspire your peers, give others insight, you don't have to hide away. Become the leader and don't be held back by the fear of wanting to express yourself or stand up for something you believe in. The judgment of others should not hinder or prevent you from wanting to have speak your mind or have fun. You should be able to do what you want to do because YOU want to. Stop trying to confine yourself to your surroundings if they choose not to do anything. That's their choice, not yours so you should do what you want to. Don't make irrational decisions, but don't let anything confine you from what's on your mind and what you want to put in action.
Even in the little things:
If no one is dancing at a party and you want to, then do it.
If no one is singing out loud and you want to, then do it.
If no one signed up to volunteer, be the first one.
Be uniquely you, you will attract people will like you for who you are if you express it.