My experience with guidance counselors was mixed. Some were great. Some were marking days on their retirement calendars. None of them knew me well enough to suggest careers which might take advantage of skills and interests I had. One time we were given the Kuder test, which takes answers to questions and applies degrees of confidence as to how applicable your personality was to various jobs. I think my list included mathematician, engineer, bricklayer, florist, and librarian. Hmm.

On the other hand, the library at school had a book from the federal government on careers (548.2: Steamshovel Operator) which described jobs, necessary qualifications, expected employment outlooks, and the like. It was useful to pore past 122.24: Civil Engineer and 761: Blacksmith to jobs I'd never heard of before. If nothing else, it sparked my imagination. And there were scads of books in that library titled something like "So You Want To Be A <fill in job>?" Maybe they were dated but they were a starting point.

I believe Alvin Toffler was right:
The illiterate of the 21st century will not be those who cannot read and write, but those who cannot learn, unlearn, and relearn.
I owe my career in IT to that quote, because what I ended up doing for a living was nothing that people expected computers to do when I was choosing a major.