This may sound very obvious, but you'd be surprised by how few people actually live by this law. If you want to be more caring, then you have to be kind and thoughtful toward others, and think of how you would feel if you were in their shoes. You may not care much when you make a rude comment to your waiter because you're cranky, but think about how the comment would make him feel. You may not care about being rude to your little brother, but you should think about how your words really affect him. Making a habit of putting yourself in someone else's shoes can make a big difference in how you see the world.
You may not be down on your luck, but someone else may be. Try to imagine what that's like before you're brusque or uncaring to someone who is less fortunate than snake game