If you've given your child a smartphone it's wise to set it up so it's safe and secure. Here's how to do just that.
Step One: Enable A Password
A password helps protect the information and accounts on a smartphone, and that's vital for any smartphone "owned" by a child. They're not notably good at remembering all of their possessions at any given time, and in an environment such as a school there's also the potential for bullying from an unlocked device. While some newer smartphones support measures such as fingerprint sensors, every smartphone supports passcodes. Here's how to create them for each smartphone type.
iOS
Go to Settings then TouchID & Passcode to set a passcode.
Android
Go to Settings then Lock screen and security and then Screen Lock Type. Depending on your precise model you may have other options, but for a PIN-style passcode, choose (not surprisingly) PIN.
Windows Phone
Go to Settings then Lock screen to set a passcode.
Step Two: Disable In-App Purchases
You can ignore this step if you're rich enough that you just don't care what your kids spend on My Little Pony digital accessory in-app purchases, or whatever your kids are into. The chances are you're not quite that rich or stupid, so locking down your child's ability to wildly spend your money makes a lot of sense.
iOS
Go to Settings then General then Restrictions. You'll have to enable Restrictions, which requires its own unique passcode. From there, you can toggle the ability to make in-app purchases available.
Android
Go to Google Play then Settings and then Require authentication for purchases.
Windows Phone
Go to Store, and then tap the three ellipses button. Then head to Settings, where you can set a PIN for music, app and in-app purchases.
Step Three: Disable Installation Of New Apps
iOS
The method for blocking new app installs is the same as for IAP restrictions. Go to Settings then General then Restrictions. You'll have to enable Restrictions, which requires its own unique passcode. From there, you can toggle the ability to install new applications altogether.
Android
App installation on Android will depend on the version of Android you're using, with older releases unable to specifically block app installation for existing apps on an account, although if you've set up a PIN block for purchases that will stop new apps being purchased from a device.
If you're using an Android tablet running 4.3 or newer, you can set up a distinct user profile with app restrictions, but on Android smartphones there's no such facility for now.
Windows Phone
The same controls that block IAP purchases can be used here; as a reminder that's by going to Store, and then tapping the three ellipses button. Then head to Settings, where you can set a PIN for music, app and in-app purchases.
Step Four: Investigate Other Measures
Quite how much further you want to protect your child's smartphone will depend on the precise circumstances of its use, with everything from outright snooping applications available to install, slightly less invasive apps for smartphone location when mislaid, such as Apple's "Find My iPhone"m and even dedicated environments such as Windows Phone 8's Kids Corner setup. There's a rich variety of kid-friendly loaders and environments on Android, although some of these are either device or manufacturer specific.
Just as there's no one-size-fits-all solution to other parenting issues, how much further you go depends largely on what you're after and what you're comfortable with. Bear in mind, however, that a device that your child has access to is one they have access to when you're not around — and prepare accordingly.