People often smugly use the term "common sense" to belittle people and make themselves feel better. "Ha! That's common sense, that person is an idiot for not knowing it!"
But perhaps some tidbits of knowledge aren't as common as some people think. Everyone probably has a set of things that they think should be "common sense", and I'm sure if we compiled everyone's list then we'd end up with several encyclopedias worth of information.
So here is my list. It is separated into categories. A lot of the things probably aren't common sense, but I think they should be. I may even be wrong on a few things (and if I am let me know), but the goal is to compile a list that is a fairly universal guide of good things to know in order to live a good life (or at least not a bad one).
In no particular order...
Science and Mathematics
-Exponential growth/decay is the most important mathematical concept to understand (more on this in the "Economics" section). You probably weren't paying much attention when you learned it in high school (unless you were a nerd like me) and that's more than likely costing you now.
-The law of conservation of energy is a good thing to think about when confronted with a bizarre claim. It can quickly help you determine if something is BS or not. My favorite example of this is if someone complains that they *can't* lose weight because of a genetic disorder. My response is always "well, if you ate zero calories for an expended period of time and didn't lose a pound, then we should study your body and find out what's going on there, because you hold the secret to unlimited energy."
-Newton's 3 Laws of Motion are good to know and understand.
-Evolutionary biology/psychology is a fascinating field that explains a lot of the weird things you think, do, and feel.
-Using ctrl+C and ctrl+V has probably saved me years of my life, and makes my mom think I am some kind of wizard.
-Everyone should learn to write a computer program in a language like C at least once in their life. You'll discover that computers are not nearly as smart as you were led to believe (but twice as sinister).
-Almost anything can be done in a spreadsheet (even without macros).
-The aggregate of all human knowledge exists on the internet, so only ask someone something if you want to make conversation.
Home and Auto
-Find the water shutoff valve for your toilet (it's usually below the tank to the left). In the event of a toilet overflow, turn it clockwise until it's tight (trust me, you want this locked into your memory so that it's second nature once your toilet starts overflowing).
-The most important part of replacing a car tire is to loosen the lug nuts BEFORE jacking up the car. It's hard to get enough leverage otherwise.
-A car needs its oil changed every 5,000 - 10,000 miles. The "3,000 mile rule" is mostly outdated (and was never based on science to begin with). Refer to your owner's manual for when to change yours.
-Don't let a mechanic trick you into changing your engine and cabin air filters! It's a massive ripoff. You can buy the filters and do it yourself in literally 5 minutes, and (in my car at least) it doesn't even require tools! There's probably a YouTube video on how to do it for your particular car.
-When driving, the right lane is for driving the speed limit, and the left lane is used for passing. If there are more than 2 lanes, then the more left one goes, the faster one should go. This is obviously not common sense because it infuriates me on a daily basis.
-Every now and then, take a look around your home and imagine if you were someone you admire walking in and seeing it for the first time. Then tidy the place up as if that person was coming over.
-Carbohydrates, fats, and proteins are all essential macronutrients for survival. Be skeptical of diets that make you cut way back on one or more of these things.
-Drink enough water so that your urine is clear (or close to it). It may be more than 8 glasses a day, it may be less.
-If you're a man and you want to be muscular, then you have to lift heavy things and eat accordingly.
-To lose weight, you have to eat fewer calories than your "maintenance" level (the amount of calories at which you neither gain nor lose weight). Keep in mind your maintenance level changes with your weight, muscle mass, age, stress level, and other factors, so your diet will necessarily have to change to adapt to these factors. Everything is in reverse if you want to gain weight.
-When you say you want to "lose weight" you probably really mean that you want to "lose fat". More than likely, you'll have to lose weight in order to accomplish this, but not all weight loss is productive (you can probably drop ~5 pounds in a day by not eating, not drinking, and taking a bunch of laxatives, but that's not exactly productive weight loss).
-Vegetables are probably important, but I think you have to wait until you're old and have some major health problems to understand how important.
-You should brush your teeth twice per day and floss once per day. Don't eat or drink anything (don't even rinse your mouth out with water) for 30 minutes after brushing, as this washes away the fluoride.
-If you're a man, visible abs don't count if you're skinny (i.e. no arm/chest/leg/back muscles). If you're a woman, no one cares if you have visible abs (most find it unattractive).
-Most doctor appointments still have to be scheduled by phone or in person. Why they don't have online scheduling by now is beyond me...but maybe one day...
-You'll go crazy if you don't get outside often enough.
Remember how I talked about exponential growth/decay earlier? Well it can either make you rich or poor...
-Credit card debt accumulates exponentially with (in most cases) very high interest rates. Always pay credit card bills in full if you don't want to become very poor, very fast
-There's a rule of thumb that inflation increases by about 3% per year. This is a good thing to keep in mind with investments and income: if you aren't growing your wealth/income by more than 3% per year, you're actually losing money.
-In order to retire, you have to invest in something. Money left in savings will be eaten by inflation. Investing in stocks/bonds/real estate/cryptocurrency/other stuff are all ways to allow the value of your wealth to increase exponentially. If you invest in diversified stocks and bonds, then you can retire with an annual salary of 4% of your invested wealth per year. For example, if you have $1.25 Million invested in stocks and bonds, you can retire on a salary of $50,000 per year for theoretically the rest of your life. The younger you start investing and the more frugally you live, the younger you can retire.
-Trying to control the economy of an entire country has always ended badly.
-Money is only one form of currency. Others include time, influence, love, happiness, intelligence, etc. Some people are very rich in some but very poor in others.
-Unlike the physical law of conservation of energy, there is no law of conservation of wealth. If you buy a product that you like from a company, are you less wealthy? They gain some money and you lose a little, but you gain a product that you presumably wanted. They get what they want (more money) and you get what you want (a good product). Both of you become more wealthy as a result of the transaction.
-Learn the concept of opportunity cost. It'll make you think twice before driving to the other side of town for cheaper gas.
(These are based on American government, so you should probably understand how your country's government works if you aren't American)
-There are three branches of government: legislative (senate and house of representatives), executive (president, advisers, other departments), and judicial (supreme court). The legislative writes laws, the executive passes or vetos those laws, and the judicial analyzes those laws. The system was designed so that no one entity has complete authority, thereby preventing abuse of power. It has kinda worked over the years...I guess?
-The electoral college elects the president, and the electors from each state are determined by the majority of votes in that state. A candidate winning the national popular vote does not necessarily mean that they are elected president. Anyone paying attention during the 2000 or 2016 elections should hopefully know this. The system was intended to not allow a large collection of people in a single area to determine the president for the entire country.
-There is probably more corruption at lower levels of government because people tend to care about national government more. So keep up with the actions of your local government and call them out when they need it.
-A successful system of government should be able to tolerate the wrong people being in positions of power. If a system of government relies on having good leaders, then it's a bad system.
-Whenever there are politicians that you like in office, there is a tendency to wish they had a large authority to pass laws/regulations that you want. Before you wish that, consider the very real possibility that a politician you despise will take their office eventually. Would you want them to have the same power?
-Know the difference between countries that build walls to keep people out, and ones that build walls to keep people in.
-It's a bad idea to invade Russia in the summer and not get out before the winter. Ask Napoleon and Hitler.
-Guerrilla warfare is a time-honored method of doing more with less. It relies on home field advantage, adequate terrain to provide cover, and some creative weapons. Lots of outside funding doesn't hurt either. The goal is not to defeat the enemy, it's to make them think twice about the benefits of invading your country. See: Russian invasion of Finland, Russian Invasion of Afghanistan, American invasion of Afghanistan, Vietnam War.
-America became a country because colonists were fed up with high taxes, and used their guns (and a lot of support from France) to overthrow the British government.
-WWI happened because Europe was divided into major alliances and everyone freaked out when archduke Franz Ferdinand was assassinated. Germany had also been developing a massive military that it was itching to use.
-WWII happened because Germany received 100% of the blame for WWI, and was forced to pay war reparations that collapsed its economy. Then a guy came along who told everyone that it wasn't their fault...
The moral of the story: don't blame people for things that weren't entirely their fault, and don't listen to a guy who says he can make all your problems go away.
Fashion and Style
-90% of how good you look in your clothes is determined by how well those clothes fit you.
-A good casual wardrobe is a necessity. Don't look like a homeless person when you aren't going to work or a wedding.
-Don't wear athletic shoes when you aren't doing something athletic. No, walking to the store is not athletic.
-Master the French technique of browning food in a pan (developing a fond), then pouring wine or some other liquid into the same pan (deglazing), then reducing that liquid until it forms a nice sauce. It will help you make 90% of the recipes out there. Like the French, it is both smart and lazy. Smart because it helps develop some intense flavors, and lazy because it means you don't have to clean the pan afterwards (if you've done it right).
-Nonstick cookware is really only helpful when cooking fish or eggs. For everything else use either cast iron, carbon steel, or stainless steel.
-Good cookware is worth the investment.
-You don't really have to actually read all the famous books, you just have to understand the basic premise enough to make conversation with people. Same goes for movies, you don't have to watch all the famous movies, you just have to be able to pick up quotes or references to them.
-It's good to be able to do at least a couple famous accents and/or deliver a funny line from a movie flawlessly. It tends to make people laugh. If it doesn't, you either aren't doing it well or need better friends.
-It's good to be able to recognize the famous works and know some basic tidbits about the lives of these artists: Michelangelo, van Gogh, da Vinci, Dali, Pollock, and Warhol.
-Beethoven's 5th Symphony is the one that starts out "dun dun dun dunnnnnnnn..." Knowing the name of the piece is good for times when you want to sound snooty.
-"Stairway to Heaven" by Led Zeppelin is the quintessential rock ballad (although it's not #1 on my list).
Philosophy and Religion
(I didn't really study much philosophy in college so this is perhaps a weak area of mine)
-Plato's Allegory of the Cave is a classic philosophical thought experiment that one should consider. If you've seen The Matrix, you've pretty much gotten the jist of it.
-Philosophy is mostly just thinking about stuff, so a lot of things can fall under the umbrella of "philosophy".
-The more different views you get on a certain topic, the closer you can get to the truth.
-If you can't argue the other person's side, then you should reassess the validity of your opinion.
-The three pillars of debate are ethos (argument from authority), pathos (argument from emotion), and logos (argument from facts and reasoning). Knowing how to properly use all three is helpful in engaging with people whom you are trying to persuade.
-If you live in America it's good to know some of the main stories of Christianity and Judaism, even if you don't practice either of these religions.
-Don't bring a knife to a gun fight.
-Finding water is the most important thing if you are stranded somewhere. In most cases it must be purified before drinking.
-"He that fights and runs away, may turn and fight another day; but he that is in battle slain, will never rise to fight again"
Hope you found this useful. I know I probably left out a lot of stuff, but there are a lot of useful things to know, probably far too many to include in a single blog post.
Any corrections, recommendations, or clarifications please leave in the comments!