Make lots of predictions and write down your thought process (seriously write them down!) once the result is in, analyze whether you were right. Were you right for the right reasons? Were you wrong but had the right thought process mostly?

Do it every day for years.

I tried this! Made a list of long-term (10y I think) predictions. Posted it on social media so that I can come back to it later, and also so that it's public & keeps me honest. And by social media, I mean "Google Circles" - tells you everything you need to know about my long term predictions, I guess...