I recommend reading Kevin Mitnick's book The Art of Invisibility: The World's Most Famous Hacker Teaches You How to Be Safe in the Age of Big Brother and Big Data https://www.amazon.com/dp/B01NC39SM6/
This is a good introduction to OPSEC
The Art of Invisibility: The World's Most Famous Hacker Teaches You How to Be Safe in the Age of Big Brother and Big Data https://www.amazon.com/dp/B01NC39SM6/ref=cm_sw_r_apan_Y8J36RD6KQTNYGQQCWA3