The smallest pile is the stuff agents sign, the stuff editors gobble up, the thins you see on bookstore shelves and on the best seller list. As many books as there seem to be out there in print, this pile compared to the first pile, is tiny. This is the stuff I lose sleep over when I come across it in the slush pile.
|things in the small pile make me happy
It's the third pile that is the most difficult. Some manuscripts come to us and they are not horrible, but nor do they stand above the rest with a blinking neon sign that reads AWESOME (like plain pasta noodles, pretty good, but won't wow your taste buds, could do with some spicing up). Your writing is good, voice is relatable, dialogue is natural, plot is probably unique, grammar is tight.
So why is your manuscript getting rejected if it falls into the third pile? It might be that you haven't found the right agent for it. Many times, it's a matter of finding the one agent who will work with you on the ms to bring from pile three to the land of AWESOME.
But, that might never happen. So you're looking at another revision. Sadly, agents cannot give feedback on everything they read (it'll happen, but not often). If you have racked up a few rejections on your partial or full, write down all the advice the agents did give you. Hopefully this is enough to let you know where to head next. If you've gotten no feedback (perhaps they gave you hope like "good writing," or "unique plot," or "amazing characters") then it might be time to ask for help.
Help comes in many forms. Critique groups are invaluable, especially when you find a great one (yes, there are bad and good critique groups). Look online if you can't find a local one to connect with. Contests many times have an editing prize. Even the first page or first five pages will significantly help your writing. The majority of conferences will have a book doctor on staff or manuscript critiques with agents and editors--do it. You'll get a good price to meet with the editor and you'll make a good connection with them (especially if they like your work). Pay an editor to edit and give professional feedback--shop around a lot when in the market for an editor. Get someone with many years experience in your genre. Many agencies have started a manuscript editing/consulting/critiquing line to their business to help writers get out of the slush pile--they will be some of the best editors you'll ever get.
The biggest thing to remember when you're in this third elusive pile: don't despair. You're doing something right. But writing is hard work--and nothing worth doing is ever easy. So keep working at it. The beauty of being in a business like this is that everyone here is here because they love it--you have support and the resources. Put them, and your passion, to good use.