what is the best way to use login module ?

[eluser]überfuzz[/eluser]
The boring but healthy answer is your own log in is the best for your site.

Personally I use a login controller and a auth library working in CI. This however is a result of the form_validation helper. It's not possible to run a form validation external. Well I like this particular helper to must to skip it.

1.a The controller login.php runs the form_validation.
1.b The custom rule callback__process_login can be used.
1.c This function uses a log_model to search the database for user.

2. The auth library is used to restrict areas, redirect when 403, log out, etc. (Reachable from every controller.)