Surround yourself with happy people. Leave the angry ones for Mars.
Say a two-line thank you prayer each day. Even if you are a nonbeliever, gratitude helps.
Take out a few minutes to do something for someone – call up an old person, make tea for your house help, help someone park the car...
Have happy thoughts and broaden your lips to smile. People might think you are a moron smiling to yourself, but believe me; it does wonders to your happiness.
Be a good listener. That can mean so much to someone and make you happier. (I don't think there are selfless good deeds.)
Sing aloud. It lifts you up. A lot.
Exercise, dance or jump around. Your body will thank you and your stress levels will come down drastically.
All these methods are tried and tested. I have only one aim in life – to be the happiest person I know. I think I am getting there. Are you?