I realize that this is a very basic question, but I feel like the Developer Documentation is missing the obvious - where do I place hook and/or Filter code? I can see a definition of the syntax but no direction as to what file it need to go into, if it is in the functions.php whether the <?php and ?> tags should be removed, etc. I've searched and searched through the forums to see some references, but there isn't clear direction.
So where do I put Hooks and where do I put Filters?