What are your best Emacs tips?

Here is a very specific tip for doing literate programming with org-mode:

Usually you put a code block like this in the .org file and generate the actual source file with M-x org-babel-tangle.

    #+begin_src emacs-lisp :tangle "init.el"
    (setq make-backup-files nil)
    #+end_src

The file name doesn't have to be a string constant, you can also call an Elisp function: (the org-prefix is recommended or you will have issues with HTML export)

    #+begin_src emacs-lisp :tangle (org-my-tangle)
    (setq make-backup-files nil)
    #+end_src

The function could look like this: ("no" means don't tangle this block)

    (defun org-my-tangle ()
      (if my-flag
          "init.el"
        "no"))

Or like this: (a more complex example using named, optional parameters)

    (defun org-my-tangle (&rest args)
      (let ((file (or (plist-get args :file) "init.el"))
            (sys (plist-get args :sys)))
        (if (or (null sys)
                (eq sys system-type))
            file
          "no")))

This will tangle to init.el on any system:

    #+begin_src emacs-lisp :tangle (org-my-tangle)
    (setq make-backup-files nil)
    #+end_src

This will tangle to init.el on Linux:

    #+begin_src emacs-lisp :tangle (org-my-tangle :sys 'gnu/linux)
    (setq make-backup-files nil)
    #+end_src

This will tangle to foo.el on Windows:

    #+begin_src emacs-lisp :tangle (org-my-tangle :file "foo.el" :sys 'windows-nt)
    (setq make-backup-files nil)
    #+end_src

I use this approach for example to generate different Emacs configurations for different platforms and use cases (private, work, ...) all from a single org file.

Incremental gains.

Get the basics, then follow your nose to the features you want to try. Before you know it you'll be writing your own stuff and sharing it.

The community is the best around.

Uncommonly useful: I have a file with two functions that I want to not just see side-by-side, but with a diff.

`C-x 4 c' runs the command clone-indirect-buffer-other-window Now you can narrow both buffers to the two different functions (mark and C-x n n) and do M-x ediff-buffers to get a diff

See also https://karthinks.com/software/batteries-included-with-emacs...

Also, rectangles: https://karthinks.com/software/more-batteries-included-with-...