Simply add following code to your theme functions.php
function better_default_post_content( $content ){
if( empty( $content ) )
$content = "Default Template is here!";
return $content;
}
add_filter( 'the_editor_content', 'better_default_post_content' );
With “the_editor_content” filter you can filter WordPress TinyCME editor value for changing values. In this code i added a filter for that.
It’s so simple if you know WordPress action filters. you can read this for action filters: http://wpcandy.com/teaches/how-to-use-wordpress-hooks/