How to query a particular page or post in WordPress

Querying a particular page or post and pulling back some of the content.

$id = 19;
$pg = get_post($id);
$excerpt = $pg->post_excerpt;
?>
<h2><a href="<?php echo get_permalink($id); ?>"><?php echo get_the_title($id); ?></a></h2>
<?php
echo '<a href="'.get_permalink($id).'">'.get_the_post_thumbnail($id, 'homethumb')."</a>";
echo "<p>" .$excerpt. "</p>";
echo '<a href="'.get_permalink($id).'" class="btn">Read More &raquo;</a>';