If you dont want to use a plugin for changing your excerpt style you can copy/paste those functions you need and to put them in your themes functions.php file.

// Changing excerpt length (default 55 words)
function custom_excerpt_length($length) {
	return 100;
}
add_filter('excerpt_length', 'custom_excerpt_length');


// Changing excerpt 'more' text (default […])
function custom_excerpt_more($more) {
	return '...';
}
add_filter('excerpt_more', 'custom_excerpt_more');


// Adding an excerpt more link to auto generated excerpts
function custom_auto_excerpt_more_link($more) {
	return ' <a href="'. get_permalink() . '" rel="nofollow">' . 'Read more' . '</a>';
}
add_filter('excerpt_more', 'custom_auto_excerpt_more_link');


// Adding an excerpt more link to manually generated excerpts
function custom_manual_excerpt_more_link($more) {
	if( has_excerpt() ) {
		$excerpt_more_link = ' <a href="'. get_permalink() . '" rel="nofollow">' . 'Read more' . '</a>';
	}
	return $more. $excerpt_more_link;
}
add_filter('get_the_excerpt', custom_manual_excerpt_more_link );