I think this is a very important topic. Clearly the real goal would be a general algorithm that would allow young people to decide on their career paths in such a way to have maximum positive benefit to society. Such an algorithm would necessarily give different answers in different cases (i.e. it obviously could not output "do math research" for everyone - that would be a catastrophe).

I don't know how to design that algorithm, but one heuristic rule I think would be useful is to ask: "are you independently wealthy?" If so, you should think more about careers in low-paying areas like mathematics, physics, literature, or art. If not, you should think about how to become wealthy (then your kids can become poets).

Overall, I think more people should be encouraged to pursue quotidian careers in areas that actually build tangible wealth, like construction, manufacturing, import/export, and traditional business (i.e. not dot-com or biotech). The fact that we don't encourage more people to do this kind of work stems from our weird cultural fascination with "education" and "knowledge industries".