Apple deserves some credit for creating consumer electronics that excite people so much that they're willing to camp out days and weeks just to buy them. It also means that people are more than willing to steal them, and if that happens you might lose a lot more than just a phone. You could easily lose your identity, your personal data, your money, and the trust of your friends.
What to do if you've already lost your iPhone
Let's start with the worst-case scenario: You've already lost your iPhone and you haven't secured your device with a passcode or set up Find My iPhone — Apple's excellent anti-theft tool. Unfortunately, once the phone is out of your hands there's precious little you can do to help get it back.
Without any protection on your phone, the most important task is mitigating the damage to you. Deactivate the phone with your network provider to prevent the thief from running up a lot of charges on your bill. Some providers will deactivate your device on their network, which prevents a thief from just resetting the device and slapping in a new SIM card.
Note that once you deactivate service, you won't be able to communicate with your iPhone via Find My iPhone. But again, this scenario assumes that's not an option.
Next, you should begin taking steps to prevent the thief from accessing your personal information on your iPhone. Begin by visiting the web presence for every app and service on your phone and seeing if they have the option to logout other devices, revoke tokens, or de-register mobile devices. This will prevent the thief from simply firing up an app or a website and using your saved login information.
If you can't find an option to prevent mobile logins, simply reset your passwords. This will be much easier if you have a password manager, but if you don't, now's probably a great time to look at getting one (Dashlane and LastPass are two good options).
Filing a police report, with the understanding that it's unlikely the police will be able to act on the theft, is a key step. Documenting the case is important, especially if the device turns up later on. Be sure to include a unique identifier for your device, such as its phone number or better yet the serial number.
Finally, inform your friends and family of the theft. It's possible that the thief may try to impersonate you through social media or via SMS on a different phone. By letting the people in your address book know that you've got a new number, you can prevent them from being victimised as well.
The best thing you can do to prevent your phone from being lost or whisked away by a thief in the future is to set up an iCloud account and activate Find My iPhone on your iPhone. To do so, simply tap settings, iCloud, and then scroll down to the Find My iPhone toggle at the bottom of the screen.
Once activated, you'll be able to remotely lock, message, or wipe your device from the iCloud web portal or from another iOS device with the Find iPhone app.
More importantly, you'll be able to remotely activate your device's GPS radio and see where it is in close to real-time. If you take this to the police (you're not Batman, let the pros take care of it) you're far more likely to get your phone back.
While you're at it, set up your iPhone to store its backups on iCloud so you can quickly and easily re-activate a replacement phone. When connected to iTunes, you can also configure your iPhone to encrypt its backups and include login information. Whichever method you employ to back up your phone, make sure you do so often, lest you miss critical information.
Beyond iCloud, take the time to set up at least a four-digit passcode on your device. While brute-forcing a passcode this short won't take very long, iPhones will automatically lock themselves for increasing durations when incorrect codes are entered. This could give you the time needed to lock it down through iCloud. It will also prevent a thief from simply unlocking your phone and shutting off Find My iPhone.
If you're very security minded, consider changing the Require Passcode setting to Immediately. You can also choose to enable a much longer passphrase instead of the default four-digit passcode, making your phone much harder to crack open. To activate complex passcodes, tap Settings, General, Passcode Lock, and toggle Simple Passcode off. You'll be prompted to create a new passphrase, one that can include more than just numbers.
Thieves are most likely after the device itself, though personal data could be icing on the cake. However, the contents of your phone that are most precious are probably your irreplaceable photos. You can create a running online backup of the last 1,000 photos through Photostream in iCloud, though this will delete old photos once you exceed the first thousand. If you're on a Mac, set up iPhoto to sync with Photostream so your pictures always have a home somewhere.
Alternatively, you can automatically upload images to services like Facebook or Flickr for backup and sharing. Dropbox also has strong integration with iPhone photos, and in at least one case has provided a startling look at the life of an iPhone thief who didn't realise that every photo he takes appears in his victim's Dropbox.
Secure your iPad or iPod touch
iPads are problematic devices, since some do not have cellular radios. This means you can't rely on your wireless provider to help lock them down, nor can you send commands to the device at any time using Find My iPhone. Be absolutely sure that every Apple tablet you have is locked down and register on Find My iPhone as soon as you can.
For iOS devices without cellular connections, it's critical that you start communicating with them as fast as possible before a thief transports them away from a Wi-Fi network. While Find My iPhone will alert you once a device re-appears, that could be a long time or simply not at all.
To its credit, Apple has a number of valuable tools in place to help you recover and secure a lost or stolen iOS device. Unfortunately, they universally require that the device be configured before you need them. While it might slow you down at first, taking the time to set up an iCloud account, enable passcodes, and use a password manager, is well worth the effort. These powerful tools could mean the difference between losing a device (and getting it back!) or losing your identity.