The average person posts so much personal information online, via social media, that if they stepped back and looked, they would probably freak out. You can build as pretty solid and highly accurate ‘profile’ if you can aggregate their info via several sites.
Your best bet, if you are going to have an online presence, is easy… Don’t over-share personal events, check-ins, any type of financial info like bitching about how high your taxes were or talking about investments. So much about you and your habits is already out there and is VERY telling about who you are, where you live, income, place of employment, relatives, friends, and if you are like most Americans, a list of possible password recovery choices.
Also, use burner accounts, have multiple and separate social media accounts that don’t tie together through a common username or even a common location. Use sites like Reddit with the attitude of 50% of your posts being how things could be vs are. Keep Twitter accounts for business, politics and socializing EACH.
Hardware and software protection. Have a great VPN, an amazing pair of antivirus software programs. Do NOT use your Facebook or Google account as a form of registering and signing in. Use multi-factor authentication login protocols. Use multiple and unrelated usernames across different platforms and finally, watch who you befriend or who follows you.
Then there are people like myself… I share, overly at times, but I have things on lockdown behind the scenes. I’m also a former deputy who has a LOT of contacts in cyber crimes investigation and tons of geeky IT security friends who thrive on using their self declared “Weaponized Autism” to find people…
Finally, never forget that EVERYTHING you put on the net, stays on the net somewhere… The Wayback Machine is just the beginning of what is really stored. You’re never truly anonymous.