I now have two teenage children. As most parents of teens can attest, this is often a cause for introspection. Therefore, without further ado, here's a list of things I wished I'd known when I was a teenager.
It's not illegal to drive without shoes on. In fact, only one state in the nation -- Mississippi -- mandates shoes for any form of non-commercial motor-vehicle usage, and they simply specify you must be shod to ride a motorcycle.
All humans have a distinctive smell. You can't smell yours, and typically neither can your immediate family, but everybody else can. Deodorant and daily -- sometimes twice-daily -- showers moderate this, but don't eliminate it. The most typical smell is whatever you eat a lot of. I -- according to some very candid co-workers -- usually smell like bacon. This would be a problem if I were in the wild and likely to be eaten by predators.
Facial and body hair retains odors. That's part of the job. That's why most girls smell much nicer than boys: they have less hair, and often trim or shave regardless. If you can smell yourself and don't want to, invest in a good pair of electric clippers. Yes, you can reach every spot on your back if you are creative.
Nobody else thinks about you as much as you do. Not your parents, not your siblings, not your friends, and least of all those who dislike you. So stop worrying about what they think about you! If you are on someone's mind, you'll usually hear about it.
People may like or dislike you for any reason or no reason at all. You can't control anybody else's emotions. That doesn't mean "don't try", though. You can turn an enemy into a friend with diligent, regular attention and care to the relationship. The easiest way to get this going -- documented by Benjamin Franklin -- is to ask them for a favor. Getting them to loan you something that you return when you said you would, along with a polite thank-you note, works really well for this purpose. It can be a textbook, a hair curler, a computer memory stick, or something along those lines. It must not be of such low value they won't miss it, nor of such high value they would refuse to loan it to you. They'll convince themselves they actually like you because otherwise why would they loan you something? At least as long as you return it with your thanks this method works amazingly well, and you may well create a life-long friendship as a result.
People may like or dislike you for any reason or no reason at all. Before attempting to convert a foe into a friend, you may want to list out the Pro and Con reasons for having them as a friend. You may just decide you'd rather not have them as a friend.
Some friends aren't worth keeping. If after every time you hang out with them you get in trouble, feel drained, or get caught up in their drama, it may be best to distance yourself from them.
If a member of the opposite sex creates their own special, non-offensive nickname for you that nobody else uses, that means they are romantically interested in you. This is true even as an adult. A weak protest at this appellation, along with a smile, laugh, or assignment of your own nickname for them in response, is an indicator of returned interest.
Small problems can become big ones. Don't ignore aches and pains; document them and be aware of your own health history. A massive infection in my tonsils nearly killed me at seventeen. Learn how your body responds to everything.
If you want to be strong with bigger muscles, teenage years are ideal for this development. Every time you sit down to eat anything, just eat some protein along with it, such as meat, poultry, eggs, or fish. Lift increasingly-heavy weights 2-3 times a week, and focus on building muscles in your back, butt, and legs. Building size in those "core" muscles makes it easier to build size in the arms, chest, and elsewhere. There are many, many variations on this theme, so if you choose to follow someone's muscle-building "program", remember that all good muscle-building programs have these core teachings in common, and it's important to try out a number of different options before deciding one or the other is "the true way" to do it.
Teenagers are extremely impressionable. If you find someone who will pay attention and talk with you, and makes you feel understood, it's extremely easy for that person to manipulate you. Beware any individual with an agenda who does so.
Related to the last point, there's a reason evangelistic (recruit-seeking) movements are so popular with young people. It's because your brains aren't finished developing until around age twenty-five. If they can lock you into a way of thought as a teenager or young adult, it's very likely they will have you for life. Typical movements include any of an extraordinary number of religions, ways of eating, lifestyle choices, sexual behaviors, and more.
Critical thinking is your best friend as a teenager. Your hormones go absolutely crazy during this time. When your body is screaming that you really want to have sex with that attractive person over there, at times like this it's possible for logic (reason) to help you act in a way consistent with your goals, rather than consistent with the impulse of your testicles or ovaries. Critical thinking really comes into play BEFORE you end up in difficult situations, by helping you avoid them in the first place.
A lot of people will tell you that the math you learn in high school is stuff you'll never use again. Depending on what you choose as a career, this may be true. About one in five people will use those skills regularly as an adult; those people are often highly-paid. In many aspects of my career, I often feel as if I get paid for my mastery of basic high-school math.
You can't get fat from eating fat. You get fat from eating starches & sugars (carbohydrates) and some other inflammatory and hormone-producing foods. If you find you need to lose a few pounds, ditch the refined carbohydrates (breads, sugary foods, etc.) from your diet. Your body will thank you.
You'll go a long way toward mastering your appetite if you understand this concept:
"People overeat because they are getting fat."
The choice of foods you eat push your body to make itself fat or lean by changing its hormonal environment. If you choose poorly, your body begins to store fat, depriving your muscles and organs of vital energy, and you feel hungry all the time. If you choose wisely, you remain satiated and can trust your hunger to indicate when you actually need to eat.
Drink when you're thirsty. The whole "eight glasses of water a day" thing is a guideline, not a rule. During light activity and average or cold temperatures, your body will typically tell you when you need to drink. The two exceptions are when you are engaged in heavy exercise or it is very hot. Create a strict hydration schedule to ensure you need to urinate at least every hour when you're dealing with extreme heat or exercise.
People will sometimes tell you not to drink caffeinated beverages when you're thirsty because it's a "diuretic". "Diuretic" means "makes you need to urinate". WATER is also a diuretic. Water is your best and safest choice, but don't be afraid you're going to suddenly shrivel up and die from dehydration due to a can of Diet Coke. You won't; the very slight diuretic effect of caffeine is indistinguishable from water in average concentrations (that of a cup of coffee or less).
Don't drink sugared sodas or eat candy. They really, truly rot your teeth, brain, and body. If for some reason you do, engage in some light exercise right after ingesting it, and brush your teeth within 60 minutes.
Baldness is going to hit 3 out of every 4 men in life, some of them in their teenage years. It's better to plan for it and be happily surprised later in life than it is to fret about it. Most treatments have nasty side-effects, and shaved or close-cropped bald heads -- aside from the requirement to wear a hat outdoors in sunshine -- look great.
Most teenagers, if provided a car, will wreck it, typically when alone or with other new drivers in the car. Learn the public-transportation system in your area well, keep your bicycle in good repair yourself, and practice driving regularly your first year with an experienced driver at your side if possible.
Stuff a handful of bills into your sock and go sightseeing around your hometown with a friend a few times a year. There's a lot more to see and do close to your house than you ever imagined.
Choose your values; don't let your values choose you. If you believe something, question why you believe it, then ask yourself and others to analyze your questions.
Correlated point: choose your anti-values, don't let them choose you. If you disbelieve or are opposed to something, question why you disbelieve it, then ask yourself and others to analyze your questions.
You tend to mimic your friends, and they tend to mimic you. This applies to many things, including lifestyle, diet, behavior, and appearance. Be aware of whatever values you choose.
There are a zillion different religions on the planet. In my opinion, each has a specific reason for existing, and understanding the niche that religion fills for people is very helpful to gain insight about yourself and humanity as a whole. Before deciding one religion is the "one true and only way" due to the happy accident of your birth, why not explore as many as you reasonably can for a year or two? You'll make a much more informed decision. If you're of the Judeo-Christian persuasion, I think it's very helpful to remember that Jesus didn't choose to be baptized until he was an adult of around thirty years of age.
Well, there's more, but that's all I have for today.