These tips that have all worked for me. They aren't hard, and we can usually manage at least one each day.
• Connect each morning with the natural world. This can be done on the way to the car or to the bus or on the way to work. Quiet your mind just a little and let yourself notice that tree in the next yard, or the lake as you drive by it on the way into town. Let yourself feel a sense of wonder that we live in a world that includes such amazing things. This is easily done with delicious food, too. A moment to marvel that we live in a world that includes chocolate, well...
• Surround yourself with happy people. When we surround ourselves with complainers and worriers, we learn how to complain and worry. When we surround ourselves with happy people we learn how to be happy. Watch what they do, how they live and what they say.
• Do a Metta (Lovingkindness) meditation every day. If you have trouble finding time, do a short version in the shower. Offering a genuine wish for all beings to be happy raises the "happy" factor in your own life. You'll find an example here.
• Practice saying something kind to somebody every day. Keep track that you do this every day. Do it especially with people you don't like. Just be sure it's authentic. It gets easier, and gives amazing results.
• Say a Gratitude meditation at bedtime every night when you say your prayers. To fall asleep with a positive thought makes for sweet dreams and a happier awakening. You can find one on this page.