The Domain Name System, or DNS, is a great way to track users. DNS converts human readable names, like Facebook.com into numbers like 126.96.36.199.
Changing DNS is a little more technical than installing a browser extension, and two services offer an alternative to letting ISPs watch everywhere I surf, OpenDNS and Cloudflare.
Using an alternative DNS often speeds up the internet, as it routes web traffic through their servers rather than V*rizon, C0mcast, or whomever. For some years I have used OpenDNS, but they were bought by C!sco, and their vibe changed, but their service is still good for home users.