Mobile
Cloudflare
Install Cloudflare on your phone, which will at least anonymize all DNS queries. Just go to: https://1.1.1.1 and it'll lead you directly to the app. After installing the app just toggle the button in the app to direct all DNS queries through Cloudflare.
Or, depending on your version of Android, you can go to the network settings for your device and set the private DNS there.
DuckDuckGo Browser
Now I'm recommending you necessarily use the DuckDuckGo Browser, but do install it on your Android device. Then go to Settings and scroll down to and enable App Tracking Protection. As I understand the tracking protection happens ON DEVICE, which is very important. This is a much easier set up then NextDNS.
NextDNS
NextDNS is a great mobile solution for anonymizing DNS queries, but also to squelch many tracking services. After setting up NextDNS on your phone there are a host of protection services that you can enable. Please read about them and the services they provide and choose those that suit you best.
Don't use these apps!
For mobile phones follow all the other recommendations made on this site, but the main thing I want to advise here concerns apps.
Don't install or use apps that are going to suck every bit of information they can about you, your activities, your location, etc. In particular I would not install or use any social networking app: Facebook, Twitter, Instagram, whatever. This is rather difficult to do since most phones come not only with such apps pre-installed, but you can't even remove them. Lesson one: buy only flagship phones. Don't buy a phone that has crap-ware installed by the manufacturer, provider, etc. Difficult, but possible.
If your phone does have such apps, at least on Android, there is a way to disable the apps.
If you want to use some social networking app, do it through the browser! And don't use the stock browser!!!
Privacy Check App
Recently I have discovered the Exodus Privacy app for Android. I highly encourage users to load this app and let it provide information on all the trackers and permissions required by your apps. It's a eye-opener just how intrusive and privacy abusive apps can be.
You can also do a search against their database of your apps at:
https://reports.exodus-privacy.eu.org/en/
If an app you want to check with Exodus is not showing up, install Classy Shark! It will evaluate any app and provides much more data.
NetGuard
NetGuard is a firewall for apps. Through it you an designate which apps have internet access, whether through your mobile or through a wifi.
Shelter
Shelter is a tool for isolating certain apps into a "sheltered" enclave, also called the Shelter. All apps that I don't want running unless I specifically launch them, I put in the Shelter and designate them for "auto-freezing." Freezing them just means that those apps so designated will only run, when I unfreeze and launch them. Always remember to freeze them after using them.
/e/ Foundation
Because any Android phone and it's apps are snooping on you and selling your data, I also encourage users to look into more opensource and privacy-concerned versions of Android. Lineage OS has been around for a while and is a good alternative. But my current favorite is /e/ Foundation. You can check them out at: