Even if you work with the absolute best in premium WordPress themes, you will undoubtedly find that you need some additional/different functions than the theme has build it. A great resource that is built in to WordPress is template tags. A template tag is basically just a way to display information. Below, I have compiled a few of the many tags that I find particularly useful.
---------------------------
edit_post_link
This tag gives you a link on the post page to the WP dashboard to edit that particular post. One of my favorite things about this post is that it does not show up unless you are logged in. To your users, they see nothing, but it allows you to easily edit posts you are looking at.
Usage*
<?php edit_post_link( 'edit', '<p>', '</p>' ); ?>
---------------------------
the_author_posts
This tag will tell you how many posts a particular author has posted. This could be a nice touch on an author archive.
Usage*
<?php the_author(); ?> has blogged <?php the_author_posts(); ?>
Harriett Smith has blogged 425 posts.
---------------------------
single_cat_title
I like to use this tag in my single.php file to display the category of an individual post. I generally use it at the bottom.
Usage*
<?php single_cat_title( 'Currently Browsing' ); ?>
Currently Browsing WordPress.
---------------------------
wp_login_url
You could use this tag in your header or footer (anywhere really, I am just recommending using it somewhere that appears on every page) to provide a login link to the WordPress Dashboard. This can be especially handy if you run a site with lots of people logging in.
Usage*
<a href="<?php echo wp_login_url(); ?>" title="Login">Login</a>
---------------------------
get_avatar
Ok, I’ll be honest. I only included this one because I really want to see the movie Avatar. This tag will get the avatar of anyone who left an ID or email address. Commonly used in comments.
-matt
* All usage is copied from the WordPress.org codex page for each template.