How To Include a css stylesheet?

Hi There
I tries to include a style sheet in the plugin but couldn’t really do it –
This is the code I used –

function wptuts_styles_with_the_lot()
    {
        // Register the style like this for a plugin:
        wp_register_style( 'custom-style', plugins_url( '/css/custom-style.css', __FILE__ ), array(), '20120208', 'all' );
        // or  

        // For either a plugin or a theme, you can then enqueue the style:
        wp_enqueue_style( 'custom-style' );
    }
add_action( 'wp_enqueue_scripts', 'wptuts_styles_with_the_lot' );

Help?

http://wordpress.org/extend/plugins/print-button-shortcode/