First, make sure that 3D Touch is enabled on your iPhone. Pull up your iPhone keyboard and then 3D Touch anywhere on the keyboard. Do not remove your finger from the keyboard. This should turn your keyboard into a trackpad/mouse and you can move your finger to where you want your cursor to move. This makes it easy to edit/add to long texts that you have written.

Rather than using the typical 4-digit or 6-digit passcode, you can make sure your IPhone is even more secure by using an alphanumeric passcode. An alphanumeric code allows the usage of both letters and numbers in the formation of a custom passcode. Thus, the use of an alphanumeric code allows for a nearly unlimited number of possible combinations.
This minor setting adjustment is simple to accomplish. First open the 'Settings' app on your IOS device. From there, tap the 'Touch ID and Passcode' option, followed by 'Change Passcode'.  Once given the opportunity to submit a new passcode, tap 'Passcode Options' located above the keypad. In doing so, you will be offered further options for your passcode customization. From these options, select the 'Custom Alphanumeric Code' option, and enter your own custom code. 

In spite of being more connected to each other than ever before, Privacy concerns are a thing..
To help keep your device safe from hackers, or any other prying eyes, it’s recomended that you turn off USB accessories.
To do this, in iOS 11.4.1:
Tap on Settings > Touch ID & Passcode (or on the iPhone X Face ID)
Enter your passcode.
Scroll down to USB accessories>
Make sure it is turned OFF.
This will prevent USB accessories from connecting to your device when it has been locked for over an hour.

QR Code reader app in iOS 12 will automatically detect a QR code and display the information. Now you can also add the shortcut of QR code reader to Control Center for easier access. After adding shortcut, you just have to bring control center by swiping up from any screen and tap the shortcut for QR Code reader.

To add the shortcut, go to Settings > Control Center > Customize Controls and scroll down to tap + to the left of Scan QR Code. Now the shortcut should have been added in the Control Center.

If you don’t want the camera to detect any QR code automatically, then you can turn this off at Settings > Camera > Scan QR Codes.

With iOS 12 you have an option to enable deletion of voice memos permanently after a specific number of days. You can also choose a recording option between Compressed and Uncompressed and save the recorded voice memo by location name automatically.

To manage these settings go to Settings > Voice Memos and refer the section ‘Voice Memos Settings’.

In addition to manually enabling Do Not Disturb, with iOS 2 you can schedule the time that you would want the phone to be in Do Not Disturb mode. You can also make this schedule as Bedtime to silence all notifications and dim the lock screen during that time. There are additional settings to further tweak the calls that can be allowed when the phone is in Do Not Disturb mode.

Go to Settings > Do Not Disturb to schedule and turn on the Bedtime.

In iOS 12 you can perform quick actions by assigning Siri Shortcuts. Since this feature is still in beta, currently you can assign Shortcuts only to the Siri recommended actions. As of now, you can create Shortcuts for Shri recommended actions by recording custom voice commands. To create a Siri Shortcut, go to Settings > Siri & Search and tap All Shortcuts.

In the next screen, choose any of the activity that Siri recommends and tap + next to the activity to record the voice command. Once the voice command is recorded by tapping the red record button at the bottom, save the Shortcut by pressing Done. You can view all the Shortcuts created under Settings > Siri & Search > My Shortcuts.  Now you can perform the action that you created as Shortcut by using the voice command after opening Siri.

With the new Measure App in iOS 12 ypu can measure real-world spaces and objects using your device. 

 

You can repeat these steps again to measure multiple dimensions of the object or space. Once you complete all the measurements, you can take a snapshot by clicking the shutter button in the bottom right corner, or erase the measurement by tapping clear. App also detects the shape of an object and takes the measurement of the entire object in a single click.This App comes in handy when you want to take a quick measurement of an object or area.

With the Screen Time app introduced in iOS 12, you can check the usage of your device, set time limit for the apps, schedule Downtime. When you scheduled Downtime which is a time away from the screen, only the apps that have chosen to allow and the phone calls will be available.

 Go to Settings > Battery to check the health of your battery.  You can view the interactive charts that show your battery performance broken down by battery level and activity for the last 24 hours. 

You can also find the time spent with screen on and off over the last 24 hours or 10 days. Interactive line chart will let you know when the battery level dropped faster. By touching the line chart at that point of low battery level will show the details of the apps below that consumed the battery in terms of activity percentage and battery usage time. These stats can be viewed by tapping the header on the top of the list of apps. 

Many other settings related to battery performance available in iOS 11, such as Low Power Mode and Battery Health are available  in iOS 12 as well. 

To get public betas, you can register with Apple Beta Software Program for FREE. After registering with Beta program, you’ll be able to enroll your iOS device, Mac, or Apple TV to access the latest public betas, as well as subsequent updates, directly from iOS Software Update, the Mac App Store or tvOS Software Update. Follow the instructions to upgrade iOS in your device.

With built-in Feedback Assistant app comes with iOS public beta you can send a feedback directly from your device about the Beta. Through the Feedback Assistant app , you can report issues that you come across when using Beta version of iOS 12.

Notifications in iPhone will help you to get a quick glance of up to date information. 

But it could be overwhelming if you start to get alerts from each and every app in your iPhone. 

You can make use of notifications more effectively by managing to receive only from the Apps that are important to you. 

Go to Settings -> Notifications and tap the app from the list to turn the Notification on/off specifically for that App.  To certain extend, turning off the unnecessary notifications will help to keep the battery longer.