Online privacy is something all of us need, whether we realize it or not, but we never get enough of. Don't get me wrong, I'm not trying to sell you on paranoid theories like the government is watching you, but realistically speaking, many companies, especially IT giants such as Facebook, Google, Microsoft, Yahoo, etc. make most of their money by tracking the users. So, in case you're interested, here's are a few solutions for preserving your online privacy on a Mac.
If you're concerned about your online privacy, the first step that you need to take is to actually tell websites and online service that you don't want them to know what you're doing online. All the major browsers you can use on a Mac (Safari, Chrome, and Firefox) have a Do Not Track option in the Privacy section of their Settings, which you should always enable. Unfortunately, there are quite a few websites that won't respect the browser's request to stop tracking it, so a better solution that not many people know of is to visit the Network Advertising Initiative Opt-out page. This industry-run service will scan your current browser for running cookies, show you exactly what services are tracking you and allow you to opt out of them either individually or all at once.
Another important step in preserving your online privacy and in some cases even your personal security is to be careful with your privacy settings on the Internet services that you use: Facebook, Twitter, Snapchat, Instagram, Steam, YouTube, etc. Make sure that you don't share too much personal information, that complete strangers don't constantly know your location or where you live and that the pictures and videos that you share can only be watched by the people who are meant to see them.
As far as third-party solutions go, installing an ad-blocker will help reduce the tracking from the websites that you visit by stopping their cookies. I recommend Adblock Plus or uBlock; both of them have versions for Safari, Chrome as well as Firefox. In case you want to turn your browser into a privacy fortress, try installing another browser extension called Ghostery along with the previously mentioned ad-blockers. This add-on stops tracking tags, Web bugs and various other underhanded tracking techniques used by the websites. TOR, the privacy-focused browser, and network, is one of the most effective ways to keep your online privacy and anonymity. Even though recently, it has been proven that the network isn't as impenetrable as originally believed, it's still good enough for most of your anonymity needs, but there is a browsing speed trade-off. Lastly, a solution that I've recently discovered is something called ICLOAK; a USB dongle that will mask your online traces as well as your activity on the PC.
Before we end, you should know that online privacy is mostly a myth and you'll never be completely safe. However, this doesn't mean that we can't at least try to make it as hard as possible for companies to make money based on our online habits.