Use spaces over tabs and align function parameters or let bindings. Do not align the body of a let, if, when, etc..

(format "%s %d"
        something
        something-else)

(let ((thing1 "a string")
      (thing2 3.141))
  body)

• Introduction to emacs lisp
• https://github.com/bbatsov/emacs-lisp-style-guide