Avatar in the Header

(Sorry if this is in the wrong forum)

I’ve started my own Theme from scratch and its almost finished now. But one thing I’ve been working on at the moment is trying to add the given user’s avatar to the Header along with his/her name, link, etc. My only problem is I’m only receiving is that only the Default “Mystery Man” avatar appears. I know mine IS working and set up correctly with Gravatar.com as it appears in the Admin Panel. Here’s the code I’m using to call the avatar:

<?php echo get_avatar( $id_or_email, $size, $default, $alt ); ?>

I’m still new to the WP codex, but I haven’t been able to find any possible answers. Thanks!