Hide the Dock in Mac using a shortcut.

To hide the dock in Mac, press Alt+Cmd+D i.e. Option+Command+D combination. Press the same combination to get the dock back.

Save the captured screenshots at your favorite location.

Mac OS X keeps all the captured screenshots at desktop, by default but you can change it to your favorite location. From Terminal, execute the command defaults write com.apple.screencapture location /your location . After execution run another command to refresh the changes killall SystemUIServer 

If you want to save space on the Dock, minimize the windows into application icon.

Go to System Preferences > Dock, check the option Minimize windows into application icon. This will minimize window to their assigned application icon. Right-click the icon to select from multiple open windows. You can also run this using terminal, run defaults write com.apple.dock minimize-to-application -BOOL YES in terminal window. 

Retrieve your Macintosh HD icon on desktop.

To enable/retrieve Macintosh HD icon on desktop, click on Desktop, press Command+J, enable the option Show hard Drives

Show Item information in Finders icon View.

To get additional information for directories, open Finder > Macintosh HD >Command + J. This will open properties window. Check the option Show Item info. Now, you can get information like the number of items in a directory, the dimensions of an image, or the length of a music or video file.

How to close/quit not responding applications in Macintosh.

If you are unable to quit an application in Mac, then try to Force Quit the application. From Apple Menu select Force Quit and select the application and click the Force Quit button. Also, you can use Cmd-Option-Esc sequence to pop this menu.

How to Fast user switch in Mac.

To enable fast user switching, goto System Preferences > Accounts > Login Options , click on Enble fast user switcihing checkbox. To switch, from the menu bar click on right side where the logged in user name appears. A drop down menu will appear, click on Login Window. This will open login screen, select the user you want to login/switch.

Enable password protection when machine is wake up from sleep or screen saver in Mac.

To Enable password protection, go to System Preferences > Security > General tab and check option Require password to wake this computer from sleep or screen saver. By enabling this, it will prompt for password when ever machine is wake up from sleep or screen saver. 

Remove third-party plugins from Mail.

To remove third party plugins, make sure Mail is not running, close your Mail if it is running. Go to folder /Library/Mail/Bundles folder. Delete all the files/folders from this folder. Go to folder /Library/Mail/Bundles. Delete all the contents of the folder. Now open your Mail, it should work fine.

Restrict Safari to open pages in tabs not in new window

Restrict your web pages to open in new Tab instead of new window run following command in Terminal defaults write com.apple.Safari TargetedClicksCreateTabs -bool true Restart Safari to take effect. To revert your setting run command defaults write com.apple.Safari TargetedClicksCreateTabs -bool false 

Switch between applications.
In Mac OS if you are running lot of windows, you can bring all windows in front by using Expose. Press the F9 key and Expose instantly creates thumbnails of the open windows and displays them on screen. Click on the desire window you want and it will switch the application. You can press the F10 key to create thumbnails of the open windows of your current application. Or F11 to move all open windows to the side, so you can see the files on your desktop.

Customize your screen saver in Mac.

Goto Apple menu, select System Preferences > Desktop & Screen Saver and click on Screen Saver tab. Left column lists available screen savers. 

Add an application to the Dock

Open the Applications folder, select the application and drag it to the Dock. 

 Customize the Dock.

Select Dock from Apple menu and click on Dock Preferences, a dialog will open giving you access to all of the Dock customization options.You can change size of the Dock, select the location where the Dock should appear, Genie/scale effect, Bounce effect. 

Capture screen shots in Mac

To take a screen shot of entire screen press Command + Shift Keys +3 Press Command + Shift keys + 4, cursor will cahneg into crosshairs, now you can use to select whatever portion of your display you’d like to capture in a screen shot. If you hit the Spacebar after typing Command + Shift key + 4, cursor will replace by camera. With camera, you can take a screen shot of the Dock, the entire menu bar, a single open menu, the desktop, or any open window.

Disable images in Safari

Open Safari, goto Safari > Preferences. Select Appearance and uncheck Display images when the page opens 

Show hidden files in Mac.

Run command in terminal, defaults write com.apple.Finder AppleShowAllFiles YES 

Enable the root user in Mac OS X 10.4

From the Finder's Go menu, choose Utilities. Open Directory Utility. Click the lock in the Directory Utility window. Enter an administrator account name and password, then click OK. Choose Enable Root User from the Edit menu. Enter the root password you wish to use in both the Password and Verify fields, then click OK. Open System Preferences and click Sharing. Click Firewall, and then click Start. To block incoming traffic on ports used by one of the sharing services, disable that service in the Services pane. 

Enable the root user in Mac OS X 10.5 or later

From the Finder's Go menu, choose Utilities. Open Directory Utility. Click the lock in the Directory Utility window. Enter an administrator account name and password, then click OK. Choose Enable Root User from the Edit menu. Enter the root password you wish to use in both the Password and Verify fields, then click OK. 

To turn on firewall protection on your computer in Mac 10.4

Open System Preferences and click Sharing. Click Firewall, and then click Start. To block incoming traffic on ports used by one of the sharing services, disable that service in the Services pane.