This is a shortened version of the recent Heise.de Security checklist. It doesn't aim to make you as secure as possible but get most users fairly secure.

The short version; install updates, make backups, check what you run and use a password manager.

Windows

  • Install windows updates
  • Check your Anti Virus, activate it's updates
  • Make backups
  • Keep all your software up-to-date
  • Use Windows Firewall, mark networks as public or home
  • Use Bitlocker if possible

Android

  • Install updates
  • Check Play Protect
  • Avoid APK Files (FDroid/Yalp is okay, don't download directly)
  • Check permissions
  • Setup screen lock / boot lock

iOS

  • Install updates
  • Passcode & TouchID
  • Check permissions
  • Enable 2FA
  • Encrypt backups

macOS

  • Install updates
  • Make backups
  • Check privacy settings
  • Setup the firewall
  • Enable theft protection

Browser

  • Install updates
  • Check extensions
  • Disable plugins you don't need (Flash, Java, Silverlight...)
  • Use https:// (HTTPS Everywhere recommended)
  • Check website permissions

WhatsApp

  • Check desktop connections (Whatsapp Web)
  • Enable Backups
  • Check your public info
  • Enable 2-factor verification
  • Be vigilant!

Google

  • Don't use Google
  • Use 2FA
  • Check connected apps

Social Media

  • Don't use Facebook
  • Use 2FA
  • Check connected apps

Raspberry Pi

  • Change Password
  • Install updates
  • Make backups
  • Check scripts
  • Be careful when opening to the internet

Wifi Router / WLAN Router

  • Secure admin password
  • Use WPA3 or if not available WPA2
  • Use long and safe Wifi password, 20 to 30 characters (QR Codes!)
  • Setup a guest network
  • Check port forwards
  • Disable WPS and UPnP
  • Install updates

Smart Home

  • Change Passwords
  • Install updates
  • Secure your remote access
  • Prefer wire over wireless
  • Close data leaks, check privacy settings

NAS, Storage Devices

  • Secure Passwords
  • Install Updates
  • Disable unneeded functions
  • Enable logging
  • Encrypt everything

Backups

  • DO IT!
  • Seriously, make backups.
  • Now
  • Anything is better than nothing
  • 3-2-1 (3 copies in 2 storage containers, 1 offsite)
  • Check your backups

Passwords

  • NEVER RECYCLE
  • Better Long than Good
  • Use a password manager
  • Use notepads for sensitive passwords, keep the notepad safe
  • Use 2FA everywhere