how to show posts from specific category in wordpress

Here is the code to show all post form category.

<?php query_posts('category_name=news&showposts=3'); ?>
<?php while (have_posts()) : the_post(); ?>
	<h3 class="contentheading"><?php the_title(); ?></h3>
    <?php the_content(false); ?>
    <?php if(preg_match("/\<\!\-\-more\-\-\>/", $post->post_content)) { ?>
	<a href="<?php the_permalink(); ?>" class="readon"><?php _re('Read more &raquo;'); ?></a>
	<?php } ?>
    <?php endwhile;?>

more detail about customization please refer
Reference link http://codex.wordpress.org/Template_Tags/query_posts