You can take a screenshot.
From saving content you view on your mobile browser to taking quick snaps of funny texts, taking a screenshot can be incredibly useful in a lot of ways. Taking a quick snap of whatever is on your iPhone’s display is super quick and easy; simply press the home key at the bottom of your phone at the same time as the button at the top of the device. Your screenshot will be saved to your camera roll.
Have Fun With Siri
If you add the address for people in your contact list and then ask Siri to take you to them, she will give you directions to their house. Telling Siri about your relations will cause her to ask to remember them. If you agree, she will remember. Then, whenever you ask her to name your relation, she will. e.g. Telling Siri that Rebecca is my sister will make her tell that Rebecca is your sister whenever you ask the question, "Who is my sister?"
If you have scrolled down a really long web page, then just tap the bar on the top of your screen to immediately be taken to the top of it.
To automatically backup your iPhone on iCloud, go to Settings > iCloud > Storage & Backup and turn on iCloud Backup. This will automatically backup your phone's critical data without the need to synchronize it again and again.
To type in capital letters, just enable Caps Lock on your phone by double tapping the Shift arrow.
Extend Battery Life
If you feel that your iPhone's battery performance is below par, you can increase it by disabling 3G, Bluetooth and push notifications. Just go to Settings> General> Network to do this.
Use the Home Button
Pressing the Home button once will take you to your Main Screen. Pressing it twice will take you to Spotlight Search which you can use to search everything on your phone.
Control what appears in Spotlight search
To control what appears in Spotlight search, go to Settings> General> Spotlight Search and select according to your needs.
Block Inappropriate Content
To do so, go to Settings> General> Restrictions and tap Enable Restrictions. This will allow you to add a pass code and select which apps you want to make accessible.
Download Apps and Music on all your iProducts
If you have many Apple devices and don't want to download the same apps or music on them again and again, you can enable automatic downloads for apps, music and iBooks by going to Settings> Store.
Send Read Receipts in iMessage
You can let others know when you have read their text messages by enabling "Send Receipts" from Settings> Messages.
Close Programs Running in the Background
Just double tap the Home Button, then hold your finger down on the app you would like to close. Then, once it starts shaking, tap the red minus icon to close. This will be of huge help if you find that your phone is running slowly.
You can be a master of autocorrect.
If you are typing a note or an e-mail, you may have had some issues with the iPhone’s autocorrect or autocomplete features. Sometimes the results from this feature are helpful and right on, but other times they are anything but helpful. If you pay attention when you type, you don’t have to be at the mercy of your iPhone. A little textbox will pop up and recommend a spelling or a completed word; to accept it press the space key. If you don’t want to accept the word, tap the tiny “x” that appears next to it. This can help you avoid some faux pas when texting.
Create your own dictionary.
Speaking of autocorrect and autocomplete, you can create your own dictionary. When you enter a custom dictionary, your phone will autocorrect and autocomplete the things you type by inserting words you actually use. To do this, go to “Settings” and then “General.” In this menu, scroll down to the shortcuts area and tap “Add New Shortcut.” Not only will this let you enter in custom dictionary words, but you can also enter in shortcuts so that your abbreviations will end up inputting complete words in texts and emails.
Have custom ring tones for less money.
Your iPhone comes with many ringtones and message tones, but these are the same sounds that millions of other iPhone users are utilizing. If you want something unique, you may be tempted to shell out big bucks for custom ring tones. If you like to assign special ringtones to certain people or groups, this may cost you a lot. So, in order to get ringtones without breaking the bank (and taking away your app budget), you should look at applications that allow you to make ringtones out of songs you already have on your phone. Some of these cost money and should only be bought if you want to create a lot of ringtones. If you are only looking to turn out a couple of tones, you can even get a free version of these popular apps.
Block your number from other people’s caller ID.
Blocking your number can be helpful for any number of reasons. Maybe you don’t want an ex that you need to call to have your new number, or possibly you are using your personal number for business, but you don’t want professional contacts to have your personal digits. You can block your number easily from the “Settings” menu. There, you should go to the “phone” area and select the “Show My Caller ID” option; there you need to slide over to “no.” To switch it back on, follow the same steps and slide over to “yes.”
Multitask like nobodies’ business.
One of the reasons many preferred Android to the iPhone was because it offered better multitasking. As the iOS developed, multitasking has improved. When you need to quickly switch from one app to another, you simply have to press the home button to leave an app. Then double click the home key again to reveal your most recently used apps at the bottom of the screen. A quick swipe of the finger will allow you to flick through all recently used applications, allowing you to quickly hop from one application to another; thus making you more productive.
Related: 6 Uncommon But Highly Useful iPhone Features