On the iPod Classic, turning the shuffle feature on or off requires a trip through the system settings. Look in the Music settings on an iPhone, and you won't find any such option. To make it easier to enable and disable shuffle instantly, the iPhone positions the shuffle toggle directly on the Now Playing screen beneath the volume slider of each song in the Music app. If your songs shuffle unexpectedly even with the option disabled, turn off "Shake to Shuffle" in the Music settings.
Open the Music app from the Home screen. Alternatively, open the Control Center while in another app by swiping up from the bottom of the screen and then tap the title of the currently playing song.
Tap "Now Playing" or choose any new song from the "Songs" tab if the Music app opens to your library rather than displaying the current song.
Press "Shuffle All" on the Now Playing window to turn off the shuffle feature. The button changes to read "Shuffle," which you can tap to turn on the feature.
The iPhone has another shuffling feature, Shake to Shuffle, which picks a new song every time you shake the phone. To stop your phone from changing songs every time it moves around in your pocket, open the Settings app, tap "Music" and turn off "Shake to Shuffle."
You can shuffle any grouping of songs on your iPhone without having to turn on shuffle in advance. Pick a playlist, album, artist or genre, swipe downward and tap the shuffle icon at the top of the screen, which looks like two overlapping arrows. This re-enables shuffle across the entire app, not just for the current selection, so remember to disable it from the Now Playing screen when you finish.
These directions apply to the iPhone's native Music app. Alternative music apps such as Spotify, Amazon Music and Google's Play Music include their own shuffle settings. Some music apps including Pandora are designed to function like radio stations, so you can't pick a specific song. Similarly, you can't turn off Shuffle Play in Spotify unless you have a premium membership.
Information in this article applies to iOS 7. It may vary slightly or significantly with other versions.