If you're reading this on your iPhone, you can just go ahead and turn your brightness down. That's step one, fool.
The battery life on the iPhone is notoriously garbage. But I believe in a world where iPhones of all data plans, carriers, and colors are able to endure those prolonged Snapchat Story sessions and secret Kim Kardashian: Hollywood "lunch breaks" without losing their lives. These 15 battery-saving steps will serve as lithium metal liberators, finally freeing your battery from the shackles of that ubiquitous white box-plug thing. Here we go.
Take back control of your brightness
Duh. The brighter your phone is shining, the more battery is being sucked up. If you don't know this, owning a phone might not be right for you. Disable auto-brightness and opt for manual control of your display, bring it down to the lowest level that's comfortable for you see, then only turn it up when absolutely necessary. Go to Settings > Wallpapers & Brightness, to make it happen.
Turn off Wi-Fi and Bluetooth when you don't need them
If you know you won't be using Wi-Fi and/or Bluetooth, turn 'em off by deselecting each in the slide-up control center. If you don't, your phone will be searching for networks and bluetooth-enabled devices at all times.
Turn on airplane mode when you have no cell service
Pretty much the same idea as turning off your Wi-Fi and Bluetooth. This will allow you to access everything you'd be able to access anyway, without Wi-Fi or regular cell service, but your phone isn't wasting juice desperately searching for a signal.
DON'T close all those apps...
Contrary to popular belief, closing active apps will NOT conserve battery. In fact, frequently closing and re-opening apps will actually drain your battery. When you close an app, you take it off your phone's RAM, and reopening it forces your machine to load it back into the RAM again, using more power than if you just kept it open and running in the background. That being said, it is admittedly not good for the functionality of your phone to keep dozens of apps open. So only keep around the ones you use on the reg.
... but identify prime suckers
You can see exactly how much battery your favorite apps suck. By locating the prime suspects in the war on low battery, you'll know which ones to use sparingly. Go to Settings > General > Usage > Battery Usage.
Updating iOS and apps while plugged in
Updating an operating system or individual app is battery-depleting in itself, but these updates can fix lingering bugs that are causing drain, or implement energy-saving revisions. Just stick to updating when you're plugged in.
Disable push notifications you don't care about
Do you really need an alert every time you get a "Hot Singles in Your Area With Free iPads and Viagra!" email? Go to Settings > Notification Center to keep tabs on all those pesky pushers. If you MUST immediately know about every new Tinder match, you can augment your push notifications, leaving out vibrations, activation of the backlit display, and other battery killers. Which leads us to...
Let's face it, vibrations feel so great. But they are a capitol source of battery suckage. Aside from shutting the vibes off completely, you can actually make custom, shorter vibrations, or make sure your phone only vibrates if certain people call/text. Go to Settings > Sounds, and from there you can access your vibration settings. To customize your vibration, you need to select a specific "Sound and Vibration" option (ex: ringtone, text tone, etc.).
Don't let apps track your location
Many apps utilize your phone's GPS system, and you might not even know it. Like our government, Facebook, Yelp, Instagram, Snapchat, and even your camera have location-based features that may be running in the background and draining your juice. Go to Settings > Privacy > Location Services to see which apps are tracking you. You can simply shut off all of them, or manually pick and choose the apps that need this feature.
Don't use parallax or dynamic wallpapers
You know that really amazing feature that makes your not-embarrassing-at-all Carly Rae Jepsen wallpaper move all 3D-like behind your apps, correlating with your movements? Yeah, that's draining you, dude. Also, those continuous-motion wallpapers do the same thing. Go to Settings > Wallpapers, then click on your current wallpaper. Disable "Perspective Zoom," and you will be officially un-parallaxed.
Disable "Share My Location"
This one is very hard to find if you don't know where it is. Go to Settings > Privacy > Location Services > Share My Location. Your "Share My Location" option is almost definitely selected, and it shouldn't be if you are trying to make that battery last.
Disable automatic app updates and refreshes
By going to Settings > iTunes & App Store, you can shut off your Automatic Downloads. You can also stop automatic Background App Refresh by hitting Settings > General > Background App Refresh. This feature allows apps to refresh content, even while not in use. You are better served doing this manually, and only to the apps that you want updated.
Disable automatic uploads to Photo Stream
Most new iPhones are set up to automatically sync your photos to your Photo Stream when connected to Wi-Fi, sending them off to all your iOS devices. While this can be kinda useful for safely chronicling your horrible decisions in photo form, it's also a major battery leach. Go to Settings > iCloud > Photos > deselect "My Photo Stream."
Enable Low Power Mode when things get dicey
iOS 9 introduced a suite of pretty great new features, including this one, which automatically disables a bunch of under-the-hood power-sucks. So, when you're desperately clinging to that last 10% of juice, head to Settings > Battery and turn it on.
Give your iPhone battery a nice, healthy life
When you first get your phone, it should at least be semi-charged upon arrival. Thats's fine -- but when the charge is done, try to let it sit (while dead) for a little bit, before giving it another FULL CHARGE. It's important to fully drain and fully charge at least once a month. And as it turns out, there are quite a few other things you should be doing differently to prevent screwing up the battery in the long term.