10. If all else fails, reboot or reset

Galaxy S5 reboot/restart

Sometimes there are ghosts in the machine. And to get them out, you might just need to reboot. Just hold down the power button until you see the option to shut down or reboot. Then, shut down or reboot. That should clear out any rogue processes or stuck applications. This isn't a frequent issue these days — Android has gotten very good — but it's still a final option for cleaning things up.

For a true act of last resort, there's the nuclear option. You can factory reset your phone, wiping out all the apps and downloads and anything else that might have clunked up your phone. Or course, that'll also kill your pictures and videos and anything else saved to the phone, so be sure to back up first. (And don't forget your contacts, if they're not stored in the cloud.)

Sometimes, that's what it takes. Fortunately, it's a pretty rare necessity.