6. Enable Smart Lock
Turning on a secure lock screen as explained above is important to keep your data safe, but it can be a pain to input a code every single time you pick up the phone. You can avoid that with Smart Lock. You'll find this feature tucked away in the security menu on most devices. It includes different methods of bypassing the secure lock screen automatically. You can keep your phone unlocked when you're in a certain place (like home), when a device like a smart watch is connected, or when the phone sees your face with the front-facing camera. You can even have multiple Smart Lock modules active at the same time. So for example, you could force the secure lock method only when you're away from home and the phone gets far enough away from your smart watch to disconnect.
7. Make sure your photos back up automatically
There's nothing worse than losing or breaking a phone only to realize your photos aren't backed up. You can avoid this by simply opening the Google Photos app and following the prompts to enable auto-backup. The default mode is "high quality" and unlimited space. This compresses your photos, but they look surprisingly good. If you want to save the original image, you can opt to use your Drive storage space. You get 15GB free and can buy more.
8. Get started with "OK Google"
Google search is at the heart of all Android phones, and you can start searching at any time just by saying "OK Google." This works on the home screen and in the search box automatically, but if you go into the search settings, you can get OK Google working everywhere. In the search settings, go to Voice > OK Google detection. Just turn on the "From any screen" option and the phone will have you say "OK Google" a few times to learn your voice. Now you can use the hot-word any time the device is awake from any screen. Note: Some Nexus phones also support this when the screen is off.
9. Swipe input on the keyboard (most devices)
Tapping with your thumbs is okay as an input method, but most phones have swipe input built-in too. Give it a shot by dragging across the letters for each word. The accuracy varies by device, but you can also install a different keyboard that might suit you better. There's the Google Keyboard for a clean but somewhat limited experience, and then more complex and powerful options like Swift Key.
10. Google Screen Search (Marshmallow and higher)
If you've got a Marshmallow phone, you have screen search (previously called Google Now on Tap). This is Google's attempt to bring the contextual search out of the search UI. When you long-press the home button, Google reads the text on the screen and offers contextual actions. It might help you make a calendar appointment, look up restaurant reviews, or just perform a Web search. It can also recognize things like bar codes in photos or in the camera viewfinder. Give it a shot before you jump into another app to take care of things manually.
11. Use screen pinning
If you need to hand your phone to someone else, you don't necessarily want them snooping around in other apps. This is easy to prevent -- just pin the screen. This should be enabled by default on most devices, but if it's not, check the security menu. Tap the pin icon on any app in the multitasking interface and you can lock the screen to just that app. If you have a secure lock screen, you can require that unlock method to leave the pinned app.
12. Try a different home screen
Most Android devices have a custom UI created by the device maker (eg. Samsung's TouchWiz). That includes the home screen. This is an important part of the experience, and the default home often isn't very powerful. Installing an alternative like Nova Launcher or Action Launcher can make your device much easier to use. You can use these apps to change the icons, assign navigation gestures, organize apps, and so much more. Any time you want to change between your installed home screens, just go to the Home menu in the system settings.
13. Use power saving modes
All Android phones have power saving modes of some sort -- sometimes two or three of them. Head to the battery menu (usually just Settings > Battery) on most phones to see these settings. For example, Samsung offers a regular power saving mode that reduces screen brightness and slows the CPU, then there's also an ultra power saver that locks the device to just a few essential applications. Most phones offer basic power saving modes like the former that can be turned on automatically when the device reaches a certain battery level. This is definitely something you should set up.
14. Manage default apps
Many actions on Android will ask you to set a default app, but what if you decide you don't like that default anymore? Some phones have a dedicated default app settings menu (e.g. Samsung), but the surest way to clear out those defaults is to find the app in the app menu under the main system settings. When you look at the info page for an app, there will be a button toward the bottom to view and clear the defaults. That will let you select a new default the next time you perform an action.
15. Split-screen apps (select devices)
If your phone runs Android 7.0 or higher, you'll be able to bring up two apps in split-screen mode. To do this, all you need to do is long-press the overview button. Your current app will shrink into the top half of the screen (left half in landscape), and you can choose another app from your recent list. The divider between the two apps can be dragged to change the amount of screen real estate allotted to each one. When you're done, just long-press the overview button again or drag the divider all the way to the top or bottom. Split-screen mode is a stock feature of all devices running Nougat or higher, but some phones and tablets on older versions of Android have similar functionality. For example, Samsung's devices have a very similar split-screen mode, but it's not compatible with as many apps.
16. Customize quick settings
The quick settings are the settings toggles visible at the top of the notification panel (most devices) and in the fully expanded quick settings UI. On most devices, you can access them by swiping down twice. Customizing these is something everyone should do when getting a new device, but the way you go about it will vary somewhat. Google recently added customizable quick settings in Android 7.0, but most OEMs had that feature built-in previously. Nougat devices should all work the same way -- open the quick settings and hit the edit button. Then, long-press and drag to rearrange. The first few settings toggles you have in the list will be accessible at the top of the notification pane prior to opening quick settings. It's the same basic deal on other devices, but the location of the edit button will be different.
17. Manage apps on the Web Play Store
Google includes the Play Store client on Android devices, but there's also a version of the Play Store accessible online. For some people this is a no-brainer, but not everyone thinks to use the Web-based Play Store. You can do all the same things here that you do on your phone, but faster. Apps and games can be purchased and pushed over the air to Android. You can queue up multiple installs in a fraction of the time it takes on Android. If you've got more than one device on your account, you can pick where the app goes.
18. Identify and modify app notifications
Android's notification system is great, but sometimes it's not clear which app produced a notification. Should you ever be confronted with a mysterious notification that you can't identify, there's an easy way to figure out where it came from, and change how those notifications operate. Simply long-press on the notification and the parent app will be revealed on most Android devices. Tap the info icon to head to the app's notification settings to disable it if you like. On Android 7.0 Nougat, Google added notification settings to this long-press UI as the notifications have the app name at the top by default (some OEMs will alter this). You can block or silence notifications from that app if they've become a nuisance.
19. Screen casting
Do you have a $35 Chrome cast or Android TV? If so, you can do more than stream video to it. Android devices can mirror the entire display onto your TV, and it's essentially foolproof. On stock Android devices (and a few more) there is a Cast icon in the Quick Settings. Tap that and pick an output device to start mirroring your display. On other phones, just download the Chrome cast app and use the screen casting feature included there.
20. Make tweaks to App Standby and Doze mode (Marshmallow and higher)
Google introduced two new battery-saving features in Android 6.0 called Doze and App Standby. Doze mode puts your device into deep sleep and blocks most apps from waking it up when it's been sitting unused for a little bit. Standby blocks apps you haven't used recently from running background tasks. These both work fine on their own, but you can tweak things if you want. Doze mode is accessible in Settings > Battery > (menu) Battery optimization on most phones. From here, you can make apps exempt from Doze, allowing them to operate even when the phone sits unused. This is only necessary if the app isn't working right under Doze mode. Standby is found at the bottom of the developer options menu where it's labeled Inactive apps. This has a list of all apps on the device, some of which will probably be marked as inactive. Tap on any of them to toggle between active and inactive. Don't worry -- inactive apps become active again once you've opened them.
21. Activate guest mode for shared devices
If you want to let someone borrow your phone for a bit and screen pinning is too restrictive, you may have the option to enable Guest mode. All stock Android devices have this, as well as most phones running 5.0 or higher from OEMs like Samsung and LG. To switch to a guest account, tap the profile icon in the upper right corner of the notification shade and select the guest profile. All your data, accounts, and apps will be hidden from the guest account. There's also a Users menu in the settings of most devices to control what guests can and cannot do. Note, some carriers remove this option from the phones they sell for some (probably stupid) reason.
22. Turn on Developer Options
Google hides some of the more advanced tools in a special Developer Options menu that you'll have to enable to get at things like animation speed, USB debugging, and app standby (which I'll get to momentarily). To turn on Developer Options, open the "About phone" menu at the bottom of the system settings and find the build number. Tap on that seven times and you'll get a message that you are a developer. The dev options will now be at the bottom of your main system settings.
23. Save offline maps
Google Maps includes support for saving maps offline, and the feature was recently expanded to be more powerful. It's not easy to find, though. Find the area you want to save offline, then tap in the search bar at the top of the screen. Close the keyboard and scroll the the bottom and you'll see the option to download. The app will bring up an outline to indicate the area that will be downloaded and estimate how much space it will take up. The offline data will include streets, basic points of interest, and the ability to use turn-by-turn navigation.
24. Sideload (safe) apps
The Play Store has plenty of apps, but if you want to branch out a little, there are safe ways to do that. First, head into the security settings on your device and enable "Unknown sources." That will let you install APKs downloaded from outside the Play Store. Some of the popular ones are the Amazon App store, F-Droid, and APK Mirror. Amazon offers a fair number of paid apps for free, and F-Droid is for free and open source software. APK Mirror re-hosts free APKs so you don't have to wait on staged roll-outs and can get old versions of software.
25. Use (and remove) factory reset protection
Android 5.1 added factory reset protection to Android, which is nice should your phone ever be stolen. The thief won't be able to reset and log into the phone without first knowing your Google password. However, you might also accidentally lock the new owner out of your phone (or even yourself) if you sell it. Factory reset protection is enabled automatically when you have a secure lock screen enabled in Android 5.1 or higher. Make sure you don't reset your phone less than 24 hours after changing your Google password, or you'll trigger a 72-hour anti-theft lockout. To disable reset protection for a new user to log into the phone, just disable the secure lock screen, enable OEM unlock in the Developer Options, or manually remove your Google account in the Accounts menu (this also factory resets the phone).