Leaving your phone unlocked
Its a hassle to keep unlocking phones especially if you're the kind that keeps checking your facebook and twitter feeds every 2 minutes but this is your first line of defense if, heaven forbid, you lose your phone or it gets stolen. Androids typically have that pattern unlock screen whilst iOS has the PIN instead. Using the iPhone 5s, I am grateful for the TouchID fingerprint system because it represents the best of both worlds by providing simplicity of a single touch with the complexity of the PIN without having to lift my finger. The latest Samsung S5s also have the fingerprint scanner on the home button but it is not used for locking the phone and instead is only meant to app use (like verifying PayPal accounts) so that point is moot.
Not backing up information
Smartphones are now multi-use devices and perform additional functions of a camera, music player, map, etc. Losing a phone usually results in a lost of a LOT of information that possibly is not replaceable (i.e photos and videos). Use your phone's backup function if available and save your heartache should anything bad happen. iOS has iCloud whilst Androids have Google drive - both free options which you should be exploiting to save your data ICE.
All major platforms are also now supported by Microsoft's OneDrive which will offer automatic uploads through the individual mobile platform apps. I personally use iCloud backups for phone settings and app data whilst OneDrive for iOS handles all my photo backups to my cloud (this because I have multiple legacy OneDrive accounts with 28GB of lifetime storage)
Setting up the GPS
Did a simple test - took a friend's smartphone, searched around and launched the map application. Nearly every single time, the map/GPS application had its 'home' setting to the phone owners actual home address. Now imagine if your phone is NOT passworded/passcode locked and someone manages to get hold of it, launching the app will tell them exactly where you live and gives them an easy target for their next heist (especially if you lost your bag with your phone, wallet, house keys etc). Get the picture?
Set the 'home' location to any app you are using (Google maps, Garmin, Waze etc) to a nearby location that you know of. I mean, do you really need that GPS to tell you turn by turn directions to your house from the nearest shopping mall that you visit weekly? Else, set it to a public location like a school, mosque, temple, 7-11 etc.
Address book/Contact list problems
Yes contact lists are convenient and make you lazy at forgetting numbers but here's a tip which has relevance with the first tip above. In the same test I mentioned earlier, the contact list ALWAYS had a listing for HOME, MAMA or PAPA or something along the lines like that. Now you've all heard or read emails about horror stories that someone's parents received a phone call telling them that their son/daughter has been kidnapped and demands a ransom ... where'd they get the number? Why from your unlocked phone inside your phone's contact list of course!! How nice of you to provide these nasty people with information like this.
Taking photos
Photos are fun. Photos are useful to capture a moment in time. Selfies are also fun. Nude selfies are NOT. A smartphone in the hands of another user other than yourself may result in your embarassing photos being leaked out. All devices (unfortunately) allow the photo directory content to be viewed in any computer without even having to unlock the device.
If you want to take nudes or unmentionables at least use a encryption app - there are dozens out there you can choose from that can give you a level of privacy which your default phone camera app cannot.
Leaving apps logged in
I suffer from this habit too as I tend to leave most apps logged in - but at least I lock my phone and set it to wipe if its being hacked into. Many popular apps keep you logged in even when you shutdown the app (e.g. Facebook, Twitter, Instagram, Flipboard) and anyone with access to your phone will basically have access to those app accounts too. Worst case scenario is with banking apps. I wich app developers would incorporate additional protection features to prevent this. The only one I know of is Evernote which has an additional PIN entry aside from the normal login to prevent anyone from viewing content so you can remain logged in. For other apps, its best to log out especially if you don't lock your phone.
Not installing an antivirus and app manager
This is for Android/Windows Phone devices only. Due to the open nature of the platform and also based on a phone owner's actions, an antivirus may be necessary. If you use an Android and often sideload your apps downloaded through fileshare/rapidshare/forums/etc, you should have an antivirus app installed to reduce the likelihood that your device will be infected with malware. Windows phone devices may run on a separate build as opposed to their desktop operating systems so the jury is out on whether it is needed or not.
For androids - even with the latest releases - app management is still horrendous. You need a management app to help corral apps from misbehaving and making your device run out of resources. Always uninstall apps you never/hardly use because those apps WILL slow down the device even if they are not running (don't ask me how or why, I still can't figure that out yet)
Allowing apps to access facebook/twitter/etc
Unfortunately, this also reveals information similar to the GPS tip above. Using several posts, a stalker can pin point the exact location where you live because your start and end locations are always the same. Next, the app tells them when you are not home or when you ARE home. Personally, I wouldn't want an unknown person to know that. The right picture shows a screenshot of someone (I randomly selected a facebook user) who allowed EST to post on their page .... now I know where he lives and when he's not home.
