First thing to do is make sure there are no iOS updates awaiting installation.
If there are, run those.
Make sure you have more than 35% battery (Preferable to plug your phone into charger).
Tap Settings > General > Software Update.
Tap Download and Install. If a message asks to temporarily remove apps because iOS needs more space for the update, tap Continue or Cancel. Later, iOS will reinstall apps that it removed.
Go to Settings > General > Background App Refresh and take a look at the list. Do you really need all those apps updating themselves in the background and draining your battery life? Be ruthless and turn off all the apps you don’t need to update automatically. Remember, they’ll still update and work as normal when you fire them up, they just won’t keep running when you’re not using them. If you find that you don’t like the change, you can always head back into this section and toggle the apps back on again.
Some apps will send you notifications that you don’t really need. Go to Settings > Notification Center and look under Include. Tap on any apps that you don’t need notifications from and choose None under the Alert Style, and then toggle Show in Navigation Center to off and Show on Lock Screen to off.
You can have your iPhone update Music, Apps, and iOS automatically, but it will eat a lot of battery life. Your iPhone might also choose an inopportune moment to update everything. You can save power and battery life by going into Settings > iTunes & App Store and sliding Use Cellular Data to off, so it only updates on Wi-Fi. You’ll save even more if you just turn the automatic downloads off altogether and update on your own schedule.
You don’t need AirDrop turned on all the time either, so swipe up from the bottom of the screen to bring up the Control Center and turn it off until you actually need it.