Quora is a fantastic website and I highly recommend membership. Imagine Yahoo Answers, plus about 50 IQ points and a coalition of smart kids getting adult advice about the rest of their lives, and you have an intellectual Eden based on life experience and upvotes.
Anyway, this question recently appeared in my stream: “Life Advice: What habits would you tell me (a 13-year-old male) to start building because they proved the most useful to you?” I wound up typing a small essay for the questioner; it is replicated below. (Not that I’m an authority on life, but I try to keep to my own advice, and it has worked out decently so far).
So far, this guidance has a sample size of one; if it works for my 11-year-old brother someday, I will claim a bit more authority. Eli, you’ve been warned.
People here have said just about all the things I could say, but as a 19-year-old who didn’t really become conscious of the way he lived his life until he was 15, let me congratulate you for asking this question. Also:
1) As someone else said, keep a journal. Doesn’t have to be daily, but every few days–and between entries, keep a list of things that have happened to you that you thought were interesting. Added benefit: keeping a journal helps you think about having to report whatever silly thing you’re about to do, and also contributes to your desire to live a life worth writing down.
2) Read nonfiction in addition to “literary fiction”. The latter can be nice, but will tell you less about the world than certain well-written books full of facts.
There’s far too much good stuff out there for me to make any absolute suggestions, but I would look especially at cognitive science–the study of how to think and avoid common errors of thought. “Thinking, Fast and Slow”, “Being Wrong”, “You Are Not So Smart”, and “Predictably Irrational” are all great starting points and should be in bookstores or libraries. Others I’d recommend: The “How Things Work” books and the Wikipedia summaries of the works/authors on this list.
(Yes, summaries. These books are long, and if scientific, well behind what we know now, but if they sound interesting, you can go ahead and read them, and if they don’t, you’ll at least grasp the ideas behind them.)
3) Read a newspaper or news website once in a while. Not every day—that was the mistake I made at 13. But once in a while, since news changes slowly but does change. Look for perspectives both on the left (the Atlantic, Slate, Salon), in the center (the Economist, the New York Times to some extent), and on the sane right (the Wall Street Journal, Reason magazine online, Marginal Revolution, the Weekly Standard).
Think critically about what you read, especially in light of the arguments of the other side. Think about issues in the light of your own experience with humans, but also keeping history and cognitive science in mind. Don’t be afraid to change your mind early and often–as long as you keep reading multiple perspectives.
4) Learn to code. Really, there’s no reason not to. It’s the language of the future world.
5) In school, find the teachers who seem best at teaching and/or most knowledgeable about their subjects. They are some of your best human resources for information and informed opinions. Ask them questions related to their subjects or related to life. They’ll be good people to know at least until you reach college, and the best students are those who want to please their teachers because they like those teachers, rather than just for the grades.
6) On exercise: Yes. Do it. But unless you really love it, don’t get into the habit of long runs. Short, hard bursts of motion are best.
And you might be a little young for weightlifting (it doesn’t have really noticeable effects until one is well into puberty), but get to the point where you can do a respectable number of pushups and chinups and you’ll be in better shape than most people. This bar was my best friend (among inanimate objects) in freshman year of high school: Amazon.com: Iron Gym Total Upper Body Workout Bar: Sports & Outdoors
7) On friends: Some say that a person is the average of the five people with whom they spend the most time. This exaggerates the case, but still, look to befriend people you find interesting, regardless of their connections to you, age, etc. I regret not spending more time with people from other grades, or those in my school who weren’t at the center of my particular social group. Seek out people who have strong beliefs different from your own and talk to them about those beliefs.
That’s about all I’ve got for now, but I may add to it later. Good luck, and again, congratulations on what should by all rights be a bright future!
See the original answer, and Quorans’ commentary, here: http://www.quora.com/Life-Advice/What-habits-would-you-tell-me-a-13-year-old-male-to-start-building-because-they-proved-the-most-useful-to-you