Unfortunately some of these key combinations are forgettable, or remarkably similar to an alternative with an entirely different use. Meanwhile, in specific apps there are a whole slew of commands in the menubar which you might use regularly, but don’t yet have a shortcut assigned to. Being able to create new keyboard shortcuts, as well as edit existing ones, can therefore markedly improve your productivity.
Enter System Preferences and click the Keyboard icon. All of your existing combinations for OS X can be seen and edited under the Keyboard Shortcuts tab.
Select Application Shortcuts and click the plus symbol that appears. Decide whether you want the new shortcut to affect all apps, or just one in particular.
Enter the exact name of the menu command you want to use. If you’re unsure, open the app and use the menubar to double-check.