[RKDinOKC]

Gave my 78 yo brother my iPhone 6. He says it has all kinds of problems. Showed him how to reboot it. 99.99% of his problems are operator error. He was upset because he couldn't text people's home land line phones. He can't make it through setting up an Apple ID or even receiving Yahoo mail. He thinks any time the battery isn't 100% it needs the charger plugged in.

First, make sure you have the latest iOS and delete any apps you don't use.
The apple store will keep track of what you own so you can re-install them if you want.

Then go through the Cellular settings and turn off phone data for any apps you don't need when mobile.
Greatly reduces battery when away from wifi and reduces data usage. I rarely use over 1 GB of data per month.

Go thru the Notifications settings and turn off notifications on the apps you don't need, especially Show on Locked Screen.
The more stuff you show on locked screen, the more you are making available to others without entering you passcode.

Under Display and Brightness make sure Autolock isn't set to a ridiculously low time like 30 seconds. Keep mine at 2 minutes.