How could I execute my plugin just in frontend (not in backend)

I don’t need my plugin running through wp-admin, including wp-login. How could I prevent it? is_admin works fine but i don’t know how to ignore everything related to wp-admin (like wp-login.php).
Thanks.

Check the requested URI:

if(!is_admin()
 && strpos($_SERVER['REQUEST_URI'], 'wp-login.php') === false 
 && strpos($_SERVER['REQUEST_URI'], 'wp-signup.php') === false) { ... }

But it’s probably better to use a white-list style:

if(is_front_page() || is_singular() || is_archive()) { ... }

These 3 tags should cover pretty much all of the front-end…