This is a WIP guide on keeping your secret identity a secret online, hiding it completely, and how to prevent yourself from being doxxed. {stub}
Basics
There are many, many ways a person can reveal personal information about themselves and even more ways to do so without even realizing it. This makes it all too easy for an attacker to piece together bits of information about you, pulling them all together to find out your name, where you live, work, go on vacation... Things you do not want out there in this line of work, especially if you have angered the government with political activism (like if you live in Hong Kong and have been protesting), or angered a few too many gang members with your reporting their activities to the police.
So let us begin.
Social Media
Your secret identity should preferably not have a social media presence at all. Social media like Facebook is one of the prime places someone investigating you would look for your information. Facebook is a biggie, as it can be more difficult for those who aren't familiar with the ever-changing privacy settings to hide their details. So if you want to hide, avoid having your secret identity on Facebook or any other social media. "But, I want to talk with folks about video games or my cat without using my persona! How can I do that?" Well, you could use a fake name or internet handle that has nothing to do with your RL information or your persona. For better privacy, use a different one for each service. Don't link them.
Don't use your Facebook or Gmail account to login to things. Yes, it's convenient, but it's also invasive.
What if you already have social media under that name? Well, you should quite frankly delete them. Not deactivate, completely delete. See if you can use GDPR to your advantage.
IPs
First off, use a VPN. You can get them for free and even on your mobile devices. This will not only hide your IP address but secure your connection if you hook up to public WiFi hotspots. Make sure that it is running at all times. Set it to start running on boot, and if your laptop is set to put apps to sleep in Sleep Mode, be sure to check and be 100% sure it's on and connected before opening a browser window.
ProtonVPN - This is the best VPN hands-down. Don't bother paying a subscription unless you plan to use P2P like torrenting things, but in that case, you can use the Split Tunneling option in Settings to exclude the torrenting app. Split Tunneling is also good for excluding programs that croak on a VPN connection, but be careful with this.
Unhackable
Okay, so you can't be 100% unhackable, but you can sure as hell make it extremely difficult. You have many options to choose from here, and I'll be listing them below.
Password Manager
Using a password manager can help you big-time. Having a complex and unique password for every online account makes it so that it's A) Hard to guess your password or brute-force it, and B) If one account is breached, they can't get into anything else.
Free. Has security check-ups that let you know if you're using a weak password or if you have the same one on multiple websites. Has apps on iOS and Android.
2 Factor Authentication
This is a must. Not every service has this, but where available, use it. This way even if your password is leaked, someone can't get in the account without passing that check.[1] Stick with apps or a physical key rather than using a phone number, as phone numbers can be SIM swapped.[2]
Addresses
This one is more tricky. In order to hide your address, you need to move entirely. Do not tell anyone this address. Do not have mail sent to this address. Use a Mail Drop. This is more secure than a P.O. box because if done right, it cannot be traced back to your name or location.