From basic applications like Mail and Safari to professional editing software like Photoshop and Final Cut Pro, power users know how to leverage both the mouse and the keyboard for maximum productivity. Sometimes, however, customizations to the default keyboard settings may be necessary. Fingers don't always stretch across the keyboard and some hotkeys are easier to remember than others. Luckily, OS X has a way for users to customize menu functions - even those that don't have a set key combination - to their liking.
You'll want to start in System Preferences --> Keyboard. Look for the App Shortcuts category in the options available on the left-side menu. Click the + to add a new app shortcut and you'll get the following window:
The Application drop down allows you to choose between all the installed applications on your Mac, or you can opt to create a universal application shortcut (for example, cut/copy/paste, which is universal to any app dealing with text). Next, you'll want to specify the exact command as it appears in the menu. I specify exact because if you format it differently or spell it wrong, it won't work. Finally, you'll specify the key combination you want to use as the shortcut for the command. After you've customized several, your main Keyboard pane will look a bit like this:
In the window, you'll notice I've created a custom key combination for sending mail in Apple Mail and another for navigating between open tabs in Safari. Just these two shortcuts alone save me hours per week and countless mouse clicks.
If you're in need of hotkey scripting or more advanced time savers, you can go even further and install an application like QuickSilver or Alfred, which allow you to customize key combinations for searching indexed volumes and performing Finder tasks like launching applications and drafting new emails while outside of Mail.