The Computer People
Macs Tips & Tricks
Here is a file with a table of various keyboard shortcuts.
There is a note about “APPLICATION SWITCHER” - when several programs are open, hold down the command key ⌘ and start pressing the TAB key.
And how to use the "magnifier"...
To magnify the screen (the ⌘ + + works just for websites)
press the control key ( ⌃ ) and move two fingers on the trackpad up and down.
But you have to set it up first (or make sure it is set up the way you want).
To change the login screen picture (wallpaper).
Find a picture you like, open in in the Preview, and Export it as "com.apple.desktop.admin" in ".png" format . (You can not just rename the file, you have to export it in the ".png" format.)
To make it simple, place it on the desktop. Then copy it to "Library/Caches" folder. (You can just drag it in from the desktop).