After starting Emacs you end up in the *scratch* buffer (assuming you’ve disabled the startup message in your .emacs file). The *scratch* can be used for writing down notes and some Lisp experiments (since it uses the Emacs Lisp major mode by default).

Now, I’m not very much of a Lisp programmer, but I do use Org-mode a lot. Consequently, I found myself changing the buffer’s major mode to org-mode regularly. And Emacs wouldn’t be Emacs if you couldn’t change this to a default. So, thanks to Bozhidar Batsov over at Emacs Redux, I’ve added the following lines to my Emacs configuration file:

;; Set the default mode of the scratch buffer to Org
(setq initial-major-mode 'org-mode)
;; and change the message accordingly
(setq initial-scratch-message "\
# This buffer is for notes you don't want to save. You can use
# org-mode markup (and all Org's goodness) to organise the notes.
# If you want to create a file, visit that file with C-x C-f,
# then enter the text in that file's own buffer.