Cell phone security is a huge issue and is constantly taken for granted. Here are some ways you can almost guarantee your phone won't get hacked. (There's always exceptions to the rule or else hackers wouldn't exist)
1.) Turn your WiFi and Bluetooth off when you aren't actively using them. All smart phones are user friendly now and allow you to access device settings very quickly without ever having to go deep into your settings. Depending on your phone type, you can be assured that your Bluetooth is off by simply tapping it once to unhighlight it. This can be done with many of your network settings such as NFC, WiFi, Hotspot, Mobile Sharing, Location, and many more when you pull your screen down from the top or slide it to the left.
2.) Use a password to lock your phone screen when it isn't being used. There are so many options to choose from such as:
Biometrics - This can be your face or finger print, anything physically attached to your body that can't be duplicated because BIOmetrics...get it?
Password - any combination of letters, numbers and symbols. Never use a name or set of numbers that can be traced to something related to you without even guessing, such as your birth date, name, or address.
Pattern - Be sure to remember the pattern you create so that you don't lock yourself out of your own device.
3.) Create a backup of your files onto the cloud server of your choice. Depending on the type of phone you have and how particular you are personally will determine that. For example, most iPhone users use iTunes & most Android users use Google. There is no right or wrong server to use as long as you keep the password for your account secure; they all hold the same quality of security for your data. Backup features can be found in your phone's settings.
4.) Create a lockout setting immediately after you've chosen a password for your phone. This allows you to find your phone in the event that it is lost or stolen. It also allows you to decide what happens when you think it may have been stolen. For example, some phones allow you to locate the device when you don't know where it is by logging into your iTunes or Google account. You can also enable a featue thatl locks your phone down after x amount of failed password attempts. You can even have your phone wiped clean so that your data isn't compromised if you know you'll never phyaically get it back. That's why backing up you data on a cloud server on a consistent basis is important.