Facebook's Suggested Friends: Facebook's Suggested Friends category is usually full of casual acquaintances, old friends from high school and other random people.
Lately, however, you may have seen random suggestions of people you don't know, yet somehow vaguely recognize. It turns out, Facebook is using your phone's location to match you with fellow Facebook users who are nearby. There's a lot that could go wrong with this feature, and it's a bit creepy. To turn it off, just disable location services for the Facebook app on your phone, thereby preventing the social network from trying to play matchmaker.
Reachability on iPhones: Reachability moves the screen down so that you can more easily tap, swipe or otherwise interact with something at the top of the screen. With a double-tap on the home button, the current screen slides halfway down the display. If you don't like or but it keeps popping up by accident, go to Settings > Accessibility and turn off the toggle switch for Reachability.
Shake to Undo on iPhones: Shake to Undo is another feature many dislike but which pops up by mistake. It pops up on certain apps -- Mail and Messages most frequently for me -- and asks if I want to Undo Typing. To disable it, go go to Settings > Accessibility. You'll find Shake to Undo a few lines above the Reachability setting discussed previously.
Multi-Tasking on iPads: To disable the slide-over and split-view features on your iPad, go to Settings > Multitasking and turn off the toggle switch for Allow Multiple Apps.