The easiest way to get started is to install the package via MELPA:

(package-install 'ctags-update)

(auto) update TAGS using exuberant-ctags

 (ctags-global-auto-update-mode)
 (setq ctags-update-prompt-create-tags nil);you need manually create TAGS in your project 
 
 ;; or only turn it on for some special mode

(autoload 'turn-on-ctags-auto-update-mode "ctags-update" "turn on 'ctags-auto-update-mode'." t)
(add-hook 'c-mode-common-hook  'turn-on-ctags-auto-update-mode)
 ...
(add-hook 'emacs-lisp-mode-hook  'turn-on-ctags-auto-update-mode)




;if you want to update (create) TAGS manually
(autoload 'ctags-update "ctags-update" "update TAGS using ctags" t)
(global-set-key "\C-cE" 'ctags-update)

with prefix 'C-u' ,then you can generate a new TAGS file in your selected directory, with prefix 'C-uC-u' same to prefix 'C-u',but save it to kill-ring instead of execute it."

when you save a file ,ctags-auto-update-mode will update TAGS using exuberant-ctags.

custom the interval of updating TAGS by ctags-update-delay-seconds .

on windows ,you can custom ctags-update-command like this:

(when (equal system-type 'windows-nt)
  (setq ctags-update-command (expand-file-name  "~/.emacs.d/bin/ctags.exe")))