I need to alter the defualt feed address from mysite/feed to something else.  Not sure where exactly in the header.php I should do that.

I'm trying to set it so that certain categories don't display in the feed by using: 
http://example.com/feed?cat=-3&cat=-4&cat=-5

If there is an alternate solution to exluding categories from a feed def let me know that too :-)

Thanks!