Answer: The usual approach is to wait until something happens that you like, and then passively enjoy it until something happens that you don't like. Of course, this makes your happiness completely dependent on your encounter with people, events, and circumstances. Another approach is to actively seek out what you enjoy, and avoid what you don't enjoy. However, this keeps you moving in and out of relationships and circumstances as you decide things are enjoyable or not, and tends to make your life unstable, as well as making it hard for others to relate to you.
Since happiness is a subjective experience that comes from your personal decisions about what is enjoyable or not, you can increase your happiness by changing your decisions. One easy way is to extend your tolerance for what is acceptable in circumstances and other people's behavior. Another very effective way to increase happiness is to cut down on comparing things, because most unhappiness comes from making negative comparisons. And if you want to be happy all the time, then practice unconditional love. It may or may not be possible to live in a state of unconditional love all the time, but the closer you get to it, the happier you will be.