This is one of the most important things you can do from a security standpoint. You can either choose to update manually or turn on Automatic Updates under Settings > General > Software Update.
It's likely that you're already using Face ID or Touch ID, but just how secure is the passcode you're using? Make sure that the passcode you're using is long and isn't easily predictable.
Given how easy it is to unlock your device, it's unnecessary to display a lot of information while it's locked. Just go to settings and disable any services you don't want others to access from the lock screen.
Be cautious whenever you're about to open a link from an email or a text message. Stay way from suspicious looking websites as they may be trying to phish you.
"Find My" was previously known as "Find My iPhone" or "Find My iPad" and it allows you to track your device. Not only can it track your device, it can also send an audible chime, lock your device, or even wipe everything if you really need it. You can enable it by heading to Settings > "Your Name" > Find My and then set it to enabled.
Hackers can take advantage of an unsecured connection to steal important data from you. To disable your device from automatically connecting to public connections, head over to Settings > WiFi and make it so it asks you first without automatically connecting to a hotspot.
VPN stands for Virtual Private Network. Its task is to protect your actions online from people who might be trying to spy on you. When the data leaves your device, it gets encrypted, sent to the Internet via VPN, only to be encrypted once it reaches its destination. You should use it especially when connecting to public networks.
To jailbreak your device means to modify your device's firmware to get rid of Apple's restrictions. This means you will be able to install a third-party software and have root-level access to the operating system. This might seem great but it also makes your device very vulnerable to risks.
Apps will often ask for permission before they can access your resources such as contacts, microphone, location, camera, etc. You can always choose to deny any access if you want. Many apps usually ask for permission for specific things they need to do to function properly and you can choose "allow only when using" the app.
In case you've already given permission to an app and want to take it back, you can always do so in the Settings. It's always a good idea to go through your Privacy settings every now and then just to make sure everything is the way you like it.