I was going to post two things that have already been posted:
“Learn to type”
“Max out your 401K”
I use that one quite often.
When I was a teen, from my father: “The sooner you learn the difference between a reason and an excuse, the better off you’ll be.”
“If you a have a problem, get rid of it.”
After hearing it, I realized how many of my problems were things I chose to
to live with, not facts of life destined to burden me.
I always used to fly into a murderous rage when my parents would say this to me. Well, not really, but it would piss me off. If I knew what the answer was before I asked the question, I wouldn’t have asked it in the first place.
I’ve always followed the idea “It’s okay to criticize an action. It’s not okay to criticize a person.”
You can tell me I do stupid things, but don’t tell me I’m stupid.
Another one “It’s amazing how many people who want to live their life they want to don’t think that idea should apply to anyone else.”
“When people show you who they really are, your job is to SEE.”
“Not all those who wander, are lost.”
“You prepare for school exams and dinner parties.
You do not prepare for life. You live life.”
“The secret to life is enjoying the passage of time,
there ain’t nothing to it, any fool can do it.”
From a book I read as a kid: You can’t demand respect, you must earn it.
From my 7th grade science teacher: Don’t lean over to tie your shoelace in a watermelon patch if you don’t want to be accused of stealing watermelons.
On a lighter note:
Always hide in a place where there are a lot of the same things.
Why dust the furniture when you can wait 5 years and use a snowblower?
“Treat normal people like celebrities, and celebrities like normal people. Both will be pleasantly surprised.”
I’ve found this to be true in both cases. 
Someone told me once “You know, if you were smarter, you’d have known not to ask that question in the 1st place”. This is now distilled into the advice I give those younger than I : “Wisdom comes when you know enough not to ask the question to which you do not want to know the answer”. Perfect example “What the fuck’s crawling on my back?” Better phrasing “Get whatever the hell it is crawling on my back off, and don’t tell me what it was”. 
From my freind who is an attorney: “Once they read you your rights, you are no longer a witness chatting with some freindly cops. You are now a suspect and those police officers are no your freinds. You cannot talk your way out now, only talk your way in deeper, no matter how 100% innocent you are. Shut the fuck up other than to say - ‘I want my attorney. Am I free to go?’”
Much better than “learn to type” is “get a degree”. Better jobs come if you have a degree than by learning to type.
“Don’t worry”.
Perspective is everything.
Make every step you take be one step closer to your goal.
Engage brain before engaging tongue.
Time spent in reconnaissance is seldom wasted.
Treat anything you borrow as if it was yours.
You know, if people did that with library books and rental cars, the poor things would be in much better shape!
Never eat anything bigger than your own head.
A good friend of mine always says: People do [insert action here]. I’m a person. Therefore I can do [action] too.
This has helped immeasurably in deciding things like taking a solo backpacking trip to Europe, and moving cross-country to New York City. Anything is possible, it’s just a matter of figuring out how.
That one can backfire, unless you only loan things to people that you know have a habit of taking care of there own things.
Maybe better, is to not loan out your things, especially things like cars, cell phones, credit cards, etc.
Depends. I treat my own stuff like crap. Any car I own is there to be driven. If I own an object, I’m going to use it. On the other hand, if I’m in a borrowed car, I’ll treat it much, much better than my own car.
My mate has an old ute that I borrow sometimes. The synchro in third is shot, so I double clutch it to avoid grinding the gears. He thinks I’m mad, and he won’t be bothered. He just grinds 'em. But it’s his choice to do that. He owns it.
Tell that to my friends with English, Drama, Arts, Philosophy degrees that are stuck with McJobs 5 years out from graduation (actually now 10 years out, most of them have real jobs).
While I agree that a degree is a good and useful thing to have it’s foolish to think that any except a few are going to provide anything in the way of a marketable skill. Most require graduate work before they really become useful.
Typing is a hard skill. It doesn’t matter what the job market is like, someone will always need a typist.
Then they aren’t looking. Many Federal Professional level jobs require a BA and nothing more (for example, being a Tax Auditor) . True, it is a Government Job, but a Government Professional Level Position is hwaaaaay better than a “McJob”.
Well, this was quite a few years ago when the economy wasn’t quite so robust. Certainly in a strong market having a degree with get you into a lot of jobs.
However, when the job market is in the toilet, having an actual skill probably serves you better.
I had to take a marketing class in college. Despite the fact that I hated the idea of marketing before hand, I learned as much or more about business in that one class as I did in every other course that I took.
One of the most valuable ideas that the instructor gave to me was “you’re always marketing yourself”. Meaning that people are going to take note of your actions today and they are going to have an impact on your future. Your future is comprised of a daily series of seemingly small decisions that you make.
Your reputation is the most valuable item that you will ever control.