I have a 2 book set by Warren Fahy.  What is the best way to have them sent together for the normal 2 credits?

They are:

Fragment (Nell Duckworth & Geoffrey Binswanger, Bk 1) (in system)

Pandemonium (Nell Duckworth & Geoffrey Binswanger, Bk 2) (7 wishers)

Edited to add:  I should mention that the Wish List Multiples Rules state that BOTH books must be wish listed in order to post there.

As long as you have other WL books to list, you can list the WL one in the WL multiples thread and add a note that you also have book 1 and want to send them together.  You technically can't list it, but I've never had trouble with a note like that not specifically listing it.  I have also listed the non-WL one in the sets/series thread and the multiple bks/same author thread with a note saying would like to send it w/the other bk listed in the WL multiples thread.  I always make them into a link, so people can get there easily.  See below.

As long as you have other WL books to list, you can list the WL one in the WL multiples thread and add a note that you also have book 1 and want to send them together.  You technically can't list it, but I've never had trouble with a note like that not specifically listing it. 

NO. The rules clearly say at least 2 books in a series need to be WLed to be offered so 2 book sets with only 1 cannot be listed. Also, listing books in the thread that are not wish listed is not allowed if they don't meet that series exception. You can only mention a non-WLed book as an option (not a requirement) if it is on your Bookshelf. If you have done this and not been asked to remove the non-wish listed books that are not included in a series with at least 2 wish listed books, we just have not spotted it, please stop doing it as it is against the rules in the thread. It is not allowed in the thread to require a non-wishlisted book to be requested to get a WLed book, which is what happens when one requires a 2 book set/series to be requested together and one book is not wish listed.

As for where to offer these 2 set books with only 1 WLed book. Technically, there isn't anywhere to. The rules of the Bazaar say that no postable WL books can be offered in the Bazaar, postable WL books should be posted to they system. The only exception to that is the WL Multiples thread where they don't qualify to be listed as a set requiring a requester to take them both. But the Help Center also offers exceptions for trading boxed sets in the Bazaar, so if we see a post here and there offering sets like this with just one WL book in them, we don't bother them much unless it is a poster offering a lot of WL books that way and probably belongs in the WL Multiples thread.