Often when editing code one wishes to open a line just under the current one, which is properly indented relative to the existing code, and position the cursor at its beginning. Such a feature is present in most IDEs, such as IntelliJ IDEA, Eclipse and NetBeans. It’s usually bound to Shift+Enter. Emacs has a command open-line, which sadly behave nothing like I’d want it to - it just breaks the current line and inserts one (or more) empty line afterwards. Luckily in the land of Emacs any shortfall is correctable with a bit of Emacs Lisp. Just add this snippet to your .emacs (or .emacs.d/init.el or whatever):

(defun er-smart-open-line ()
  "Insert an empty line after the current line.
Position the cursor at its beginning, according to the current mode."
  (move-end-of-line nil)

(global-set-key [(shift return)] #'er-smart-open-line)

Evaluate the code (or restart Emacs) and you’ll be able to use M-x smart-open-line or Shift+Enter (a.k.a. S-return).

This command is part of crux (it’s named crux-smart-open-line there).