To get started, I would recommend http://www.cozmoslabs.com/557-thematic-featured-posts/
While that runs on posts tagged "featured", it can easily be modified to do different things.
I modified it to include the image thumbnail, if one wasn't available it would use a default (the else part), I was using a version of it for a while on my site but don't any longer, so this may help.
<?php
$my_query = new WP_Query( array( 'tag_slug__in' => array( featured ), 'posts_per_page' => 2 ) );
echo '<ul class="featured-posts">';
$feat_class = array();
while ($my_query->have_posts()) : $my_query->the_post();
$feat_class = array();
// Category for the post queried
foreach ( (array) get_the_category() as $cat )
$feat_class[] = 'category-' . $cat->slug;
$feat_class = join(" ", $feat_class);
?>
<li id="featured-<?php the_ID(); ?>" class="<?php echo $feat_class; ?>">
<?php
$posttitle = '<h3><a href="';
$posttitle .= get_permalink();
$posttitle .= '" title="';
$posttitle .= the_title_attribute('echo=0');
$posttitle .= '" rel="bookmark">';
$posttitle .= get_the_title();
$posttitle .= "</a></h3>\n";
echo $posttitle;
if ( has_post_thumbnail() ) { ?> <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_post_thumbnail(); ?></a><?php
}
else { ?> <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute('echo=0'); ?>"><img height="120" width="210" src="<?php bloginfo('stylesheet_directory'); ?>/images/testimage.png" /></a><?php
}
the_excerpt();
?>
</li>
<?php
endwhile;
echo '</ul>';
?>
If you wanted to modify the logic (so it does something other than grab posts with the tag "featured", then you will want to modify the parameters which can be found here http://codex.wordpress.org/Class_Reference/WP_Query
The styling to do a 3 column would all be CSS.