The only way to really improve the production and use of serotonin is through exercise, laughing out loud, meditation and other forms of relaxation like hypnosis. In fact, a great exercise for people who want to feel good more often is to imagine NEW serotonin receptors being added in their brains. Just visualize you are inside your own brain with a magic wand and every place you touch you create a new receptor.
If visualization is not your thing, just choose a form of exercise or a variety of them that you are comfortable doing regularly. You will be amazed after just a month of regular exercise at how much better you feel.