51:  How do I execute ("evaluate") a piece of Emacs Lisp code?

  There are a number of ways to execute ("evaluate," in Lisp lingo) an
  Emacs Lisp "form":

  * If you want it evaluated every time you run Emacs, put it in a file
    named ".emacs" in your home directory.  This is known as your ".emacs
    file," and contains all of your personal customizations.

  * You can type the form in the *scratch* buffer, and then type LFD (or
    C-j) after it.  The result of evaluating the form will be inserted in
    the buffer.

  * In Emacs-Lisp mode, typing M-C-x evaluates a top-level form before or
    around point.

  * Typing "C-x C-e" in any buffer evaluates the Lisp form immediately
    before point and prints its value in the echo area.

  * Typing M-ESC or M-x eval-expression allows you to type a Lisp form in
    the minibuffer which will be evaluated.

  * You can use M-x load-file to have Emacs evaluate all the Lisp forms in
    a file.  (To do this from Lisp use the function "load" instead.)

  These functions are also useful (see question 16 if you want to learn
  more about them):

    load-library, eval-region, eval-current-buffer, require, autoload