(Preamble: I wrote this a half hour ago and forgot to hit "create" so I'm not really copying the good advice above.)

I like to get patches very much. So far it's about 70:30, apply and say thanks!, bury in my inbox and avoid saying, well, I don't think you understand what's going on here and dumping 4 hours of work in my lap to sort out this idea isn't really making me happy with the universe.

Best you can do is make the patch easy to apply. Use the latest version from SVN (update: or whatever RCS the author has) or the CPAN. Use good flags for the patch like diff -uN. Include tests that mimic the style of the author. Be clear, brief, and polite in your correspondence.

Probably should file an RT ticket first if there isn't one; bug/wishlist. You can include the patch in the ticket and send a personal note to the author. It's nice to have tracking of the issue both for the author and potential users of the code. Note, some authors use Googlecode or github and ignore their RT queues but I look at tickets when trying to pick a module for something.