Example of setup with SLIME and auto-complete

slime-ac-example.el

(require 'package)

(add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/"))

(package-initialize)

(defvar my-packages '(slime auto-complete ac-slime)
  "List of packages to install automatically.")

(let ((need (delq nil (mapcar (lambda (pkg)
                                (unless (package-installed-p pkg)
                                  pkg))
                              my-packages))))
  (when need
    (package-refresh-contents)
    (mapc #'package-install need)))

(ac-config-default)
(global-auto-complete-mode)

(add-hook 'lisp-mode-hook #'slime-mode)

(setq slime-lisp-implementations '((sbcl ("sbcl" "--noinform")
                                         :coding-system utf-8-unix)))
(setq slime-default-lisp 'sbcl)
(setq slime-contribs '(slime-fancy))

(with-eval-after-load 'slime
  (add-hook 'slime-mode-hook #'set-up-slime-ac))

(with-eval-after-load 'slime-repl
  (add-hook 'slime-repl-mode-hook #'set-up-slime-ac))