How - ask yourself "Am I happy with the way things are?" If the answer if "no," which most likely it is with everyone, then ask yourself "What bothers me most?" Then "What can I do to change it, even if it's just a tiny bit?"

What - Chances are, there is something, no matter how small or how big, that you've always wanted to do for yourself. Follow that desire.

Which - If there isn't something that you know that is unique to you already, or even if it's not unique, your perspective on it is. It can be anything from some form of art to a vocation or avocation, like poetry, writing, or simply caring for someone. Thing is, you'll never know unless you try SOMETHING. Just listen to your inner voice while trying different things. Just remember, "'Can't' never did do anything!"