(More will be added, use these for now and pick up some in the reading pieces.)
These will have a benefit you on the first day and the benefits will increase to a very high level over time. To actually remap your brain (see The Mind, re: neuroplasticity of the brain), you'll need to do these, with strong attention, for six months - your brain actually changes the neuronal pathways.
The three exercises through Appreciative Living, see her article on it (and, of course, it would be good if you read the book so you can get the password to her free 28 day e-book):
Great exercises at Happier.com. See my recommendations on which to use (soon to be posted - email me if you would like it to happen sooner). Recalling-past-happinesses exercise. Recalling the key happiness experiences in your life and writing them down and writing about them creates the awareness of what makes you happy plus it gives you more "top of the mind" items to recall and see that you had much more happiness in the happiness/unhappiness balance. You would keep these in your Reminders Notebook.
USE OF THE REMINDERS TECHNIQUE
Regular daily and/or weekly reviews of key happiness producers (or unhappiness reducers) helps to ground one in greater happiness for the day and create a greater understanding and memory of what makes one happy. The primary vehicle for this is designed for easy referenceability; it will also become one of your major tools: