Many people cite bird-watching as one of their hobbies. They enjoy watching
birds going about their business, as they hunt for insects, build nests, and
sing. (The birds, not the watchers.)
  Yet how many people take an interest in watching their own species? Are not
humans even more potentially interesting (albeit in a darker way)?
People-watching, or human-watching, is free, you don't even need binoculars.
And you might learn something.
  Next time you are outside, try noticing people a bit more. See the little
differences that make humans such a varied lot. Begin to hypothesize
questions: What sort of job might this person have? What sort of house might
they live in? What kind of music or food would they enjoy? As you become
better at this, you will find yourself being able to understand humanity
better. Talk to people too; What a person says reveals much more than what
they look like. The next time you are waiting at a bus stop, or in a lineup,
you might as well make conversation with the other people. You're not doing
anything else other than waiting, after all, and it will make the time pass
faster. As you talk to people, try to get a better sense of who they are.
Ultimately you want to understand the most important question: What motivates
people? Why do they do what they do?
  Of course, the person who you are most in touch with is yourself. To be a
good human-watcher, you must examine your own self with great scrutiny. Ask
yourself why you do what you do, why you say what you say, why you think what
you think. In your heart, you will find the same vices as everyone else.
There is evil in the heart of even the youngest child. No one can be blamed
for feeling greed, or malice, or laziness. They can only be blamed for giving
in to those urges.
  I'm not saying everybody should become a psychiatrist. But human-watching
is a rewarding and enlightening hobby, a skill which will develop with
practice. And the next time you wonder why someone does something, you may be
able to understand just a little better.