Before purchasing a mobile device, there are lots of things to take into consideration in order to make an informed purchase.Consider battery lifeIf you like to use your phone for music or gaming on a daily basis, you may need to consider getting a model with a longer battery life, which generally needs to be a 3,000 mAh battery or above. Heavy users may consider purchasing an external battery for their phone to avoid running out of juice at the end of the day.Decide on an operating systemThe main operating systems on the market today are Apple iOS and Android.Apple iOS: Available only on iPhones. Apple's iOS is easy to master and offers a variety of proprietary features such as the Siri voice-controlled assistant and the Apple Music library.Android: Powered by Google. Android is the operating system with the largest selection of handsets on the market. Unlike Apple's iOS, this Operating System is highly customizable.