1. Figure out which apps are using the most battery. Go to Settings - Battery - and check out which apps are taking up the most battery life. For me, it's my messages, iHeart Radio App and Instagram that take the top spots. If you're not going to be able to get to your charger for a while, try to use your top usage rated apps less. It can be hard because clearly these are your favorites, but they're draining your battery super quick.
2. Turn auto brightness off. I love keeping my brightness up, but if I'm 30 minutes from home and forgot my charger, I'll deal with a dark screen. Go to Settings - Display & Brightness - and turn auto-brightness off. If anything, it'll help you last until you can get plugged in.
3. Shut your location services off. A lot of apps require location being turned on, and some even use your location in the background. This is SO battery draining - I tested this out a week or so ago. I started with my phone at 100%, kept location services on and used my phone as I normally would (nothing crazy; I just used my messages app, mail and Snapchat once or twice). In an hour, I was down to 72%. Not bad, but for not that much use in an hour, it's enough to be annoyed! Then I charged to 100%, turned my location off and tried the same process again using the same apps and an hour later I was at 79%. Not too much of a difference, but sometimes 7% makes a difference!
4. Use your phone from it's lock screen. When I'm super low on battery life, I lock my phone and I answer any text messages from the lock screen (swipe the message to the right - hit reply). I know the lock screen uses battery too, but this almost always makes a difference until I plug my phone in! I usually get an extra 10 or so minutes worth if I'm really low on battery doing this and if answering texts is all you need to do at the time, it works pretty well.
5. Pretend like the background app refresh feature doesn't exist. Seriously, turn it off and forget it ever happened! I hate this feature and I've never, ever used it. I could see why it's helpful and saves time from having to update your apps, but I like to pick and choose which apps I update - especially since some updates come with bugs or an interface change I hate. 99.9% of the time, I update apps right away, but sometimes I'd rather not. Keep this feature off and trust me you'll see a difference in your battery life! To turn this on/off, go to Settings - General - Background App Refresh and toggle off. I like seeing when apps update; and I like the added battery life.
6. Get an external battery or charging case. These things are life savers!! I bought this Mophie power pack right before my Europe trip this summer and it saved my life (and my phone's life) EVERY. DAY. If you've been to Europe, you know that the service isn't always top notch - especially since most international plans today just use your provider's European subdivision. My battery died sooo quick and so many times throughout the day in Italy; I was so happy that I had this Mophie battery with me! I bought mine at the Apple store right before I left and it's the best one I've ever bought/used. This isn't sponsored at all; I just really love this thing! Different sized batteries guarantee different amounts of full-charges; I bought the one that gives two full charges and honestly I get closer to 3 full charges. Best purchase ever!
7. If you aren't using WiFi, turn it off. I really never realized this until recently, but duh - turn the WiFi off if you aren't connected! Apparently our phones search for networks nonstop if it's turned on, even if you aren't near one to connect to. Say hello to an added 10%!
8. Stay away from heat. Especially in the summer, I'm sooo guilty of keeping my phone in direct sunlight. It's so hard not to but the sun hurts your phone battery at the time and in the long run too - eeesh. This is my main problem for SURE. When your phone overheats, the battery is essentially draining short term and long term. Try charging your phone without its case on, and on a hard and flat surface to prevent it from over heating while charging too.
9. Use the charger that came with your phone. They break easily, they're so easy to lose.. I know. But I've heard time and time again from so many Apple associates (when I bring my phone in to complain about the battery... the usual) that it's important to use your phone's actual charger, and if you have to get a new one - don't try and get a non-Apple version; they don't work nearly as well. It's also important not to interchange your iPhone and iPad chargers! They use different wattage's and it only hurts the battery to interchange them - as tempting as it may be.