I've wanted to try Company-Mode for a while, so I enabled it today. It's one of the rare packages available in ELPA as opposed to MELPA. Company is a completion framework that offers a popup list after a delay (or immediately when called) in the current buffer. 

(use-package company
  :ensure t
  :pin elpa
  :diminish company-mode
  :config
  (add-hook 'after-init-hook 'global-company-mode))

That's all the configuration it needs to start. From this point on I'll have popups whenever there are several options for a prefix that I've typed, or a dim suffix inline.