Love your enemies. It sounds really hard but you will have an easier life if you do. Compliment people, stand up for someone. If someone is sitting alone at lunch or doesn't have a partner, be there for them.
Don't judge by any standard other than personal merit. Judge them individually, based on their own words and actions. Don't put people down. Don't insult people. Don't constantly compare people to others (for example, don't say "my last boyfriend always.... Why can't you be the same way?"). Accept everyone. Embrace diversity.
Treat others the way you would like to be treated. It's the "golden rule" and some think it's corny, but there's something to it. There's a concept called "pay it forward," meaning that we shouldn't wait for someone to do something nice and then repay the favor. Do something nice first, whether or not that person can do anything for you.