WordPress meta description tag

it is necessary to optimize you wordpress blog with meta description tag. most of the search engine look for meta tags. however most of the blogs don’t use these tags. and the WP also don’t use this. so you can manually place this by coding as follows.

The Main Page
is_home()

A Single Post Page
is_single()

A PAGE Page
is_page()

A Category Page
is_category()

Any Archive Page
is_archive() 

<?php if (is_single()) { ?>
<meta name="description" 
content="<?php echo htmlentities(get_the_excerpt()); ?>" />
<?php } ?> 

there is tons of plugins available to do the same this. but I advise if you are a programmer or having little idea of coding, then do it manually.