I am using Emacs 26.3 with macos Catalina and I would like to type the inverted exclamation point and question mark characters. Can someone point me to a link that will get me started towards understanding how to input special characters not available on my standard MacBook Pro keyboard.
Short answer: C-u C\ spanish-prefix RET. The characters you mentioned can then be typed as
~? => ¿ ~! => ¡
Long answer: read the emacs documentation starting at Language Environments, plus the description of 'spanish-prefix' in
lisp/leim/quail/latin-pre.el to see what other characters that method supports, and to see what other input methods are available, such as