Trusting yourself has a lot to do with your gut instinct regarding certain things. Stand up for what you believe to be the right thing to do.
Recognize that you are special, no matter what. It is impossible to love others if you do not love yourself. People can see when you think well of yourself and therefore they will see you as confident and comfortable in your own skin (and will more than likely be more apt to want to get to know you better)!
Forgive yourself when you make mistakes. Every single person - EVERY SINGLE ONE - has done something that they wish they had done differently. Try to learn from your mistakes and do better the next time.
Don't be hard on yourself. Don't put yourself down.
Smile when you don't feel like it, but don't ignore the fact that everyone has bad days and everyone deserves a hug during hard times. (Including yourself...)
Be proud of the good things you do.
Be kind in all things you do. Thinking of others and helping when you can will make you feel wonderful. I promise!