I have been helping someone who has little experience with Windows or Mac, but used DOS for years ( until pretty recently ) and I've set them up with a simple Debian Linux running XFCE4 as the desktop. I've found that I have to teach them and also document a lot of basic computer idioms -- Control-C / X / A / V to copy, cut, select all, paste; but also more basic things, like the fact there are two pointers on the screen -- one for the mouse and one for the keyboard -- if you slide the mouse pointer to a specific point and press a keyboard key, the new key will not appear where the arrow is, it will appear where the text cursor is.
A big one was tabs. I had to get a couple of manilla folders and show them the actual tabs, and hold it up next to the browser with several tabs, and suddenly it snapped with them what the interface was trying to represent.
Control-A will select all of a web page, unless you are in the text entry box of a form, then it selects just the things in that text entry box.
I started writing this up in a little manual, it got to a dozen pages fast, and I haven't put very much in it.
If anyone knows of a place where some portion of all of this is written down, post a link !