How does one do a ctrl-alt-delete on a MacPro? That is the most useful function on my PC that I miss on Apple products.
There are several ways to get to the Force Quit Application menu. One is the by way of the Black Apple menu on the Menu bar on the top of the screen. One of the choices on that menu is "Force Quit...", and "Sleep", "Restart...", "Restart..." are all available, as well as "Log out [username]". Once that Force Quit requestor appears, it will show you a list of the running Apps, select the misbehaving App, and select "Force Quit." Holding down the shift key while clicking on the Black Apple menu will change allow Force Quit to the current focused App, such as "Force Quit Safari".
Under the Go Menu, you can find a listing for Utilities, that will bring up a directory listing which will include "Activity Monitor". From that App, you can see everything that is running and force quit anything you desire. . . including some system functions which is not advisable. Be sure you know what you are doing when you try using Activity Monitor. It is an interesting App because it will show what is going on behind the scenes in a Mac. You can start Activity Monitor from Spotlight Search (the magnifying glass always available on the Menu Bar at the top of the screen on the right) by merely typing ''Act" and hitting return.
Another is that every running App is on the Dock at the bottom of the screen (It may be hidden below the screen) and it will have a Force Quit option for that app if you click on the App's Icon while holding the Option Key and select "Force Quit...".
Occasionally, it is just a single tab in Safari that is locking Safari up by either having a problem with loading a script or a malicious advertising. Mac's force quit can sometimes allow you to force close a single tab without quitting Safari. If so, that tab will be listed.
Also, you can press Command + Option/Alt + Esc (on the new MacBook Pro the function keyboard will need to have been selected with the Function key) and then the Force Quit menu will come up.
And, finally, when all else fails, and you have a true complete lock up of the system, a very rare thing on a multi-user, multi-tasking Mac, hold the power button for ten seconds and force quit the hardware. That will work in every system except those where that option has been locked out by the UNIX system admin.
Some ultra secure Macs have had even that option locked out. Pull the plug on those and if it's a desk top plug it back in after 60 seconds and restart. If it's a laptop wait for the battery to run down, about 10 hours. Of course if it IS one of those ultra secure Macs, it is highly unlikely it will let you back in even then.