If you're willing to start with the raw material, this might be an interesting question to raise at Metafilter-- it's got a lively and varied commenting community.

JenniferRM:

In the meantime it seems like there is potentially a lot of prosaic stuff of the sort that various old people would like to tell young people about how "not to make the retrospectively obvious mistake I made" with respect to actions at 20, 25, 30, 35, 40, 45, 50, 55 and so on. Each of those ages makes me think of distinct sets of life challenges that I have relatively little personal experience with, but I imagine they could go a bit better if I did a little prep work in advance, guided by grounded data.

In my experience, when it comes to sincere advice from older folks, it's extremely difficult to separate the wheat from the chaff. This is both because the world is changing very rapidly these days and because, contrary to the usual saying, most people's hindsight is very far from 20/20. People are often oblivious to how much things have changed since their youth, and unable to distinguish true instances of correct and incorrect planning from random luck.

A huge problem here is that honest reflection about one's past mistakes, missed opportunities, and suboptimal decisions tends to be very painful and unpleasant, and people consequently prefer to tell themselves (let alone others!) a highly distorted and idealized story of their life and accomplishments. When they're giving advice, this problem is exacerbated by their additional propensity to signal respectability by telling an idealized story about how things should work in an ideal world, not an honest-to-God cynical story about how they really work. (For which I can't really blame them, considering how often the latter would sound crude and offensive. Of course, as with most human hypocrisy, this idealization mainly happens at unconscious levels, not as conscious deception.)

Sure, but to continue with the investment analogy, these pieces of advice would be equivalent to the advice that you should invest your money into assets with positive expected returns, and not into games of chance with negative expected gains. In other words, there exists a certain baseline level of conventional wisdom that is common knowledge, and the only people who don't follow it are those who are exceptionally irrational, unintelligent, or suffer from poor self-control. So, the problem in those cases is how to overcome irrationality and lack of self-control, not how to acquire information, which is trivially available.

In contrast, what I meant by "getting ahead in life" is analogous to investing in an exceptionally profitable way, i.e. figuring out ways to make advantageous decisions beyond the trivially available common knowledge (possibly even contradicting it where it turns out to be inaccurate). Here, the same principle that underlies the weak EMH implies that public information will be worthless unless you're exceptional in some way, since any broadly useful and unambiguous public information would already have become part of the universally known conventional wisdom.

To take one example mentioned in the post, when it comes to ROI on various education programs, you'll notice that the public information is hopelessly confused and contradictory. For each source that suggests one thing, you'll find another that claims the opposite, and also a third one that says they're both unsubstantiated nonsense. Ultimately, if you want to make a decisions better than vague suggestions of your intuition and common knowledge -- in other words, to do anything beyond merely avoiding decisions that are clearly crazy -- you either have to be exceptionally capable of assessing the available information or privy to insider information.

JenniferRM:

It would be crazy to expect to reap "extraordinary profits" from knowing the average number of years a marriage lasts before a divorce, the primary causes thereof, and the average ages and costs to each participant.

Considering how many marriages fail with very sad (and costly) consequences, having useful knowledge that would enable you to avoid such an outcome definitely counts as "extraordinary profit" in my book!

The statistics you mention are easy to look up, but when it comes to an accurate model of the causes of marriage problems and the ways to solve and avoid them in practice, this is a very good example of an issue where good advice is extremely hard to separate from the torrents of unsubstantiated nonsense that are thrown in one's face on every corner, and where it's hard to overcome one's own biases.

I'm not looking for rocket science or magical secrets, I'm looking for an honest overview of the sturdy facts upon which normal lives rest :-)

Such seemingly easy questions are often in fact extremely difficult! To get accurate answers to them, you have to fight your way through multiple thick layers of biases, rationalizations, and distortions. First you have the idealizations and rationalizations in the stories people tell themselves, then the tendency to pronounce respectably idealized opinions instead of realistic harshly cynical views -- and last but not least, your own biases that may prevent you from accepting the often unpleasant truths.