Unknown android tricks that everyone should know

• Hide your files. Android is Linux based. So, next time you want to hide a file/folder on your Android phone, just rename it and add a "." in front of its name. The item will be hidden. It will not show up in any music or video player (Walkman and Movies) and image viewer (Albums). You can view the hidden files (to rename them back) by turning on "Show hidden files" from the side menu in ES File Explorer.

        

• Stream your media wirelessly. Turn on media server on your mobile and stream your media (music, videos and photos) on all the devices (laptops and mobiles) connected to the same Wi-Fi network viaDLNA. If your phone doesn't have this feature, download BubbleUPnP for DLNA/Chromecast on Google Play.

• Browse your phone's content wirelessly. If your device supports Media Transfer Protocol (all recent Sony Xperia devices does), you can do this right away. Connect your mobile via USB cable to Windows 7/8 laptop, right click on the device in My Computer and select Network Configuration. It takes a minute or two to configure your phone. It must be connected in MTP mode to the laptop and the laptop & mobile must be on the same Wi-Fi network. Now the steps to connect phone and laptop via Wi-Fi network might differ from brand to brand. In Xperia devices, head over to Settings -> Xperia Connectivity -> USB Connectivity. You will see the name of your computer there. Tap the name and select 'Connect'. This is for Android 4.3, KitKat and Lollipop has slightly different menus in settings so navigate accordingly. If your phone doesn't have this feature, downloadAirDroid: File Transfer/Manage - on Google Play.

• Auxiliary devices via USB OTG. As described by Nagarjun Kamineni, you can connect mouse and hard disk to mobile via OTG cable. But the hard disk must be externally powered one because mobile's battery cannot supply enough power to run the hard disk. And in addition to the mouse, you can also connect wireless keyboard and mouse simultaneously! (If both of them have a same receiver, that is.)

• 'Throw' audio via Bluetooth. 'Throw' as my Xperia calls it. Not only you can listen music via Bluetooth, you can also take calls. Just pair the Bluetooth device with the phone and it is all set. This is very useful while driving, if the car's music system is Bluetooth enabled.

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EDIT: Didn't notice 'computer' in the question. Here are some little things that I know.

• Windows Key + E opens My Computer in Windows 7 and File Explorer in Windows 8 & above.
• Hold Shift key if you want to capitalize a single letter while typing rather than turning on and off Caps Lock. If Caps Lock is ON, holding Shift key results in lowercase letters.
• If you come across a word/phrase on the web in any language and want to find out what it means, here is a shortcut. Download the chrome extension Google Dictionary. Now all you have to do is to select the word or phrase and click the extension button. This is nice!

• Press Home button on keyboard to go to the top of a web page and End button to go to the bottom of a page. This goes for text also. See the last point.
• While filling out a form, or your address while placing an order online, press the Tabkey to take the cursor to the next field andShift + Tab to take it to the previous field. This is handy!
• Ctrl + Forward/Backward (not Backspace) jumps the cursor through one word. Pressing Home button will take the cursor to the extreme left of the text line and Endbutton will take it to extreme right. While editing text, as in Microsoft Word or an answer here, Ctrl + Home takes the cursor to the beginning of the document and you can guess what Ctrl + End does. Doing this while holding Shift key will select the text between the two cursor positions.
• To prevent anyone viewing a particular file (in Windows), just change it's extension. For example, if .docx extension is changed to .jpg, Windows will automatically launch default application associated with new extension. But since the file is not an actual image file, that application will simply show it as 'corrupted' or 'cannot be opened'. To view the file, you will have to drag and drop in the original application. And this trick will not work on Linux OS.
• In case your drive (local or external) gets corrupted, try running this command  -  chkdsk /r <drive letter>: in command prompt in administrator mode. It has repaired my drives all the time. However, it takes a lot of time depending upon the size of the disk and space occupied