How to make a meta box?

Imho, the fastest way would be by using the Meta Box Wrapper Class, which is a plugin by now. Download and activate it.

Next in your functions.php add the following:

$prefix = 'cheas_cool_metabox_';
global $meta_boxes;
$meta_boxes = array();

$meta_boxes[] = array(
    'id' => 'movie_reviews',
    'title' => 'Movie Review',
    //Change the next line if you want to display on another post type
    'pages' => array( 'post' ),
    'context' => 'side',
    'priority' => 'high',

    // List of meta fields
    'fields' => array(
        array(
            // Field name - Will be used as label
            'name' => 'Movie Title',
            // Field ID, i.e. the meta key
            'id' => $prefix . 'movie_title',
            'type'  => 'text',
        ),
        array(
            'name' => 'Review',
            'id' => $prefix . 'movie_review',
            'type'  => 'textarea',
        ),
        array(
            'name' => 'Link',
            'id' => $prefix . 'movie_link',
            'desc' => 'Youtube Link',
            'type'  => 'text',
        ),
    ),

);


function cheas_cool_metabox_register_meta_boxes()
{
    global $meta_boxes;

    if ( class_exists( 'RW_Meta_Box' ) )
    {
        foreach ( $meta_boxes as $meta_box )
        {
            new RW_Meta_Box( $meta_box );
        }
    }
}
add_action( 'admin_init', 'cheas_cool_metabox_register_meta_boxes' );

Now all you need to do is to call it on your post page:

Movie: <?php echo rwmb_meta( 'cheas_cool_metabox_movie_title' ); ?>
Review: <?php echo rwmb_meta( 'cheas_cool_metabox_movie_review' ); ?>
Watch Trailer for <a href="https://wordpress.stackexchange.com/questions/65249/<?php echo rwmb_meta("cheas_cool_metabox_movie_link' ); ?>" target="_blank"><?php echo rwmb_meta( 'cheas_cool_metabox_movie_title' ); ?></a>

This should do it for you, but check out the demo folder in the main plugin directory to see more examples of different meta box types