do_action( 'wp_enqueue_scripts' )

More Information

wp_enqueue_scripts is the proper hook to use when enqueuing scripts and styles that are meant to appear on the front end. Despite the name, it is used for enqueuing both scripts and styles.

Usage

function themeslug_enqueue_style() {
    wp_enqueue_style( 'my-theme', 'style.css', false );
}

function themeslug_enqueue_script() {
    wp_enqueue_script( 'my-js', 'filename.js', false );
}

add_action( 'wp_enqueue_scripts', 'themeslug_enqueue_style' );
add_action( 'wp_enqueue_scripts', 'themeslug_enqueue_script' );