It might be time consuming, but the fact of the matter is that much of the success you may find in the publishing industry comes from who you know, being in the right place at the right time and so forth.
Let's be honest. We all know that many very interesting stories are going to be passed up by the industry giants, simply because they do not appear marketable. Whether or not you and your book are marketable is beside the point...you must appear to be marketable and part of that profile is the contacts you have made. "Who would endorse your book, etc..."
But WIERD PODLINGS GUY, who should I be networking with and how. There are a number of people and ways to meet them. Contact authors...now this may seem taboo to some, but authors are people just like you are and they enjoy hearing from fans. I know of authors who have successfully queried authors for a review and ended up getting their endorsement or even a referral to an agent or publisher. Now, I don't, by any means suggest that you should begin to stalk authors for endorsements. You might contact them through blog post comments or a letter or email. You might find yourself with them on a blog tour for your work or at a writer's conference. The point is, make contacts with authors of every caliber (who can tell who will become a star in the future...your long time POD author perhaps?) Make contacts with agents if you have the opportunity, probably through another author or at a writers conference. Just remember, in an industry as competitive as this one, it's many times who you know, just as much or more as it is how good your book is!