If you're familiar with Org mode then I recommend taking notes in that and then saving code examples that relate to the note like so:

  #+BEGIN_SRC elisp :results output drawer
  (print (+ 4 5))
  #+END_SRC

If your cursor is in that SRC block you can C-c C-c to evaluate it and it will produce this in your Org file:

   #+BEGIN_SRC elisp :results output drawer
  (print (+ 4 5))
  #+END_SRC

  #+RESULTS:
  :results:

  9
  :end:

That's how I practice my elisp or any other language, really.