Your Insecurities
Advertising is notorious for playing on people’s insecurities to sell them products or services. Modern day advertising is no different. But with the data collection tools available to it, it has a slew of new methods to figure out what you’re insecure about. So it’s best to not give them any additional “dirt” on you.
Basically, avoid typing in anything you may be worried or insecure about. While you’re at it, avoid searching for anything embarrasing, too. Advertisers see this information as a goldmine — and you’ll likely find ads specifically tailored to those search results following you around the internet. If you must, at least use DuckDuckGo.