How do I exclude categories from my category lists

I got a wordpress how to book and I think it is a little out of date.. I want to exclude some categories from my category list, such as un-categorized.

My book says to find the category id and use it in this function:

<ul>
  <?php wp_list_cats("exclude=2,5,1,6"); ?>
</ul>

But I can’t figure out where to find the id. I couldn’t find anything on this site about it. also I couldn’t find a tag like the one above. The only one i found that looked similar was this:

wp_list_categories('show_count=1&amp;title_li=<h2>Categories</h2>'); ?>

How do I find the ID # and how do i add that exclude id bit to the tag above?

Thanks for any help,

amatsuki