Author and tags not displaying in sidebar

“I am trying to display the Author and Tags in my sidebar.“

And which specific template tags would this be?

Many require use within The Loop, and the sidebar would tend to fall outside of that. If this is the case, try scoping the $post object to global first before using any post loop template tags outside of The Loop:

<?php global $post; ?>
<?php the_author(); ?>
<?php the_tags(); ?>
etc...