Remember the old Ford commercial about Quality being Job 1? The same adage holds true for the book-writing business. Our books need to be as good as they can possibly be. From the story to the editing to the cover, it's our job to present the most professional package possible. Sure, an occasional typo will slip by us, our editors and proofreaders. The best thing about digital books is that those issues can be fixed and a new version uploaded within minutes. I won't say I've never done that, because I certainly have—and I'm always thankful that I can.
Once we've attended to all the various levels of quality control, our next mission as self-published authors is to do it all again. And again. And again. The best way to sell that first book is to write a second book and a third and a fourth. And one of the best parts of being self-published is the ability to get those books out in a timely manner to continue the forward propulsion of your growing career. Most successful self-published authors will tell you that the more books you have available, the more you will sell of each one. There will be cases like Catherine Bybee, who was here last week talking about her NYT bestselling self-published book Wife by Wednesday, which took off without a big catalog behind it. But for the most part, a steady climb tends to be more the norm.
On our self-pub loop (http://groups.yahoo.com/group/selfpublish/ everyone welcome!) we've talked a lot about the timing of freebies. I always encourage authors to hold off on offering a freebie until they have several other books available to benefit from the exposure. Why give a book away when you don't have other books for sale? Freebies can be very effective in building your name and readership, but they are most effective when you have plenty of inventory for an enthusiastic reader to gobble up if they like the one you gave away. (Not for nothing, but sales of other books is also how you profit from a freebie.)
Another of my favorite metaphors involving quantity goes something like this: If you were opening a clothing store, would you launch your new venture with a single pair of pants, a single pair of shoes, a shirt and maybe a jacket? Or would you want multiple styles of each item to give customers some choice? I'd think most of us would say the latter—more choice is better. So think of your online bookstore as a clothing retailer. Make sure you have plenty of inventory ready to sell before you hang out your shingle.
Other self-published authors have suggested having three ready-to-go manuscripts before you publish the first one. I think that's a good number to help you build momentum. Get them all out there simultaneously and promote them individually. If one takes off, the others will probably benefit. Remember, though, this is a marathon not a sprint and it can take a long time for even one of your books to "take off" in a meaningful way. One trend I've noticed among all the more successful self-published authors is a propensity toward the prolific. You don't necessarily have to be prolific to be successful, but you do need to be writing every day and thinking about the next product you will offer in your growing "store."
A word to the wise: Don't cut corners on editing or proofreading. If you put out a book before its time, readers will let you know with one-star reviews that stick to the book for life, no matter how many times you revise and re-upload. Remember always that QUALITY is job 1. Quantity, however, should be a close second.