Wordpress - Get post content from outside the loop

You can use get_page() to return the $post object of a static page:

$page_id = 302;
$page_object = get_page( $page_id );
echo $page_object->post_content;

Edit

Similarly, you can use get_post() to return the $post object of a post:

$post_id = 302;
$post_object = get_post( $post_id );
echo $post_object->post_content;

to get the content of the post outside the loop you can write something like this

global $post;
$content = $post->post_content;

if ( !empty( $content ) ) :
    echo $content;
endif;

If your content include shortcodes, you should use:

$post_id = 22;        
$post_object = get_post( $post_id );        
echo do_shortcode( $post_object->post_content );