I just read a very useful article with lots of practical tips: ‘How To Avoid The Self-Published Look’.
To that I add:
* If you are printing a book the traditional way, choose good, quality paper. Don’t go for bright, whiter-than-white photocopier paper, else your book will look as if it’s just come off a photocopier. Ask for paper samples, or even show your printer or paper supplier the sort of paper you like from a book whose production you admire. Better paper might be more expensive, but it will look more professional, for sure; maybe you’ll just have to charge a little more for it, or print a few less? But it’s probably better than having lots of brighter-than-white copies lurking unsold in boxes in your garage. Make your book something that people want to possess.
* A good cover. A very good cover. Outsource it, if need be. Make your book beautiful, desirable. (Some publishers could pay heed to that too. Make your book look something more than a full-page advertisement in a magazine sold at the checkout in the supermarket.)
* Understand the differences between structural editing, copyediting, and proofreading, and introduce these as separate editorial stages in your production process.
* At some point, make sure that other sets of eyes read the book. You’ll never catch everything yourself.
And oops, I see that I go against the grain on this site in at times ‘improperly’ capitalising the first letter of every word in titles, including articles, conjunctions, and shorter prepositions. I follow that style in print, but for some reason I’ve found myself using initial caps online; it just looks tidier? Not least given that in email and other online contexts we don’t always italicise titles. Well, that’s my logic/excuse. Someday, maybe I’ll go all OCD on this site and change that, perhaps. Or maybe not. Ow, one of those editor dilemmas to keep us awake at night.