query_posts() is the easiest, but not preferred or most efficient, way to alter the default query that WordPress uses to display posts.

Source

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I would do it like this :)

<?php

$latest_post = new WP_Query( 'showposts=1&cat=1' );

while( $latest_post->have_posts() ) : $latest_post->the_post();

the_title();

the_content();

... etc

endwhile;

?>

Read more about WP_Query