Subscriptions and ad space bring the money.
> there's profit in selling information of users.
Where did you read this? What news organizations are actively selling user information?
Full stop.
Analytics. At a minimum, there's going to be Google Analytics but there might be some in-house tracking tool or some kind of audience statistics package too.
Paywalls need to make sure you haven't met the limit.
A/B tests on headlines, content, and even styling mean remembering which test group you fall into.
On the analytics front, we are measuring and reporting on pages and articles at a number of levels, from audience metrics around demographics, device type, time-of-day, time-on-page, scrolling behaviour, etc to the actual articles themselves, the section/category, even the individual journalist. We have real-time reporting and statistics on the 'performance' of any article, journalist, section, etc.
Tracking and measuring user behaviour is largely performed using a number of cookies.
2) Add each news site to your browser's javascript blacklist