Apple produces their own technical tips for the Mac and iPhone. They are short how-to videos. Check them out. I’m sure you’ll find one or two that will teach you a new trick.
Over the years, I’ve chided Apple for never providing a legend or explanation for the symbols they list next to a menu command which indicate the keyboard shortcut for that command. Well, at long last, Apple has a written technical note that explains the most commonly used hierglypic symbols and tells you the keyboard shortcut for a command. Check it out.
If you aren’t satisfied with this brief visual explanation of the keyboard symbols then you might like Dan Rodney’s chart which is a more thorough list of the keyboard symbols.