Happiness can be increased by things that remind us of happy things, from up-beat music to comedies. A particularly powerful trigger of happiness are words. Read a paragraph that contains words like 'new' and 'exciting' and 'wonderful' and you will start to feel good. Happiness also increases when we decrease exposure to things that make us unhappy.
Happiness is sometimes contrasted with joy, with happiness being a state or mood and joy being the positive experience that is triggered by an event such as receiving good news or achieving a goal.