After installing the autocomplete into .emacs.d I inserted the following lines into my .emacs-file to enable it:

;; add .emacs.d to load path
(add-to-list 'load-path "~/.emacs.d")

;; enable autocomplete
(require 'auto-complete-config)
(add-to-list 'ac-dictionary-directories "~/.emacs.d/ac-dict")
(ac-config-default)
(global-auto-complete-mode t)
(auto-complete-mode t)

To get a lisp-specific autocomplete you’ve got to include ac-slime (found at github): put it into your .emacs.d-folder and include it in your .emacs-file via

;; add lisp autocomplete-support
(require 'ac-slime)
(add-hook 'slime-mode-hook 'set-up-slime-ac)

and to switch on autocomplete globally you have to apply a “dirty fix”:

;; dirty fix for having AC everywhere
(define-globalized-minor-mode real-global-auto-complete-mode
  auto-complete-mode (lambda ()
                       (if (not (minibufferp (current-buffer)))
                         (auto-complete-mode 1))))
(real-global-auto-complete-mode t)

Now only one thing is missing: the mentioned inserting of new words on the fly:

;; create and add new words to the dictionary on the fly
(when (require 'auto-complete-config nil 'noerror)
(add-to-list 'ac-dictionary-directories "~/.emacs.d/ac-dict")
  (setq ac-comphist-file  "~/.emacs.d/ac-comphist.dat")
  (ac-config-default))

• the “Ns Command Modifier” -> “meta” and
• the “Ns Alternate Modifier” -> “No modifier“.

Now you can use your alt and meta-keys as usual.

Second I did not remember immediately how to set my previous colors and styles (e.g. the background color or the mouse color) so I will sum up my solution:

• open your “~/.emacs“
• type in (and replace my colors with your own)

(setq default-frame-alist
    (append default-frame-alist
        '((foreground-color . "LawnGreen")
          (background-color . "Black")
          (cursor-color . "LawnGreen"))))

And of course Emacs is much better than vim!