The iPhone is a revolutionary device thanks to its user-friendly interface and sleek minimalist design -- but that doesn’t mean it’s always straightforward.  Many of the iPhone’s advanced or lesser-used features are hidden away and Apple doesn’t always do the greatest job of filling you in. This intermediate guide hopes to help point these features out, and is follow-up to MakeUseOf’s Beginner iPhone guide (also available for iOS5). This version of the Intermediate guide is intended for iOS6 users. If your phone is not up-to-date, read MakeUseOf’s iOS5 version instead.