In System Preferences, the Keyboard control panel lets you set up shortcuts that apply globally. Some of them are pre-assigned, but all can be changed.
An incredibly useful shortcut that I use frequently each and every day is. I prefer to set this shortcuts to (command key plus the backquote character), because that combination is relatively easy to type with one hand.
I also like to turn off a lot of shortcuts, like those for Universal Access, because I don’t use them, and they can interfere with shortcuts in other programs.