If you are going solo, or plan on using tax preparation software and need to know what schedule to file, etc, you can find a good deal of information online. Of course, like any web research, you should make sure the information is cross-referenced on different sources. Or go to The Source itself: the IRS website's self-employed page.
There are several pages of handy overviews for tax-weary writers: Moira Allen's article on Writing World, Publishlawyer.com's article on Taxes and the Writer,Authors and the Internal Revenue Code by Linda Lewis, an article on Hackman-Adams's site entitled Writer's Guide to Taxes, and Profit vs. Pleasure on the Fiction Factor site.