How do you know which field is potentially "the future" and that you are at "the leading edge" ?

To put this in perspective, these ideas seems to ring a bell for me. It is coherent with my experience growing up during the last 20+ years. When my father bought a full size portable HDD to listen to music in 2000, it seemed obvious to me that it was the future. Same for internet usage, payments, video players, smartphones... I noticed grown-ups doing entrepreneurship with these technologies and it seemed obvious that it was the best decision for them to make at the time. However, now a full grown up engineer and able to make things, I find it harder to be sure of what the future may be and what is at the leading edge. I feel like the amount of bullsh*t has exploded, maybe because I have access to more information sources and are more knowledgable. I follow HN obviously, but also producthunt [3] and more "journalistic" news like The Verge. [4] I think answers to this questions will be valuable for the HN community and for the world, so I dared to ask, even if english is not my first language. Sorry if I made mistakes.

[1]: http://www.paulgraham.com/richnow.html [2]: http://www.paulgraham.com/startupideas.html [3]: https://www.producthunt.com [4]: https://www.theverge.com