Actually, I have no advice for you on how to do that* but my friend Michelle Goodman, author of The Anti 9-to-5 Guide: Practical Career Advice for Women Who Think Outside the Cube and the forthcoming My So-Called Freelance Life:
How to Survive and Thrive as a Creative Girl for Hire (both from Seal Press) has a great post up about using blogging to build a platform for your book idea with 23 suggestions about how to go about it.
This isn't strictly about blogging but a little hint: Google news alerts are your friend! Not only that, I think they are necessity at the very least for your name and your book's name. Choose comprehensive. I have, uh, hundreds of these and they are a major source of my information about some of the topics that matter to me most. They can also fuel your blogging if you have "nothing to say." You also learn really fast what Google tracks, and what it doesn't. Comprehensive covers blogs but it's not an exact science. For example, for my name alone, I have "Bussel," "Rachel Kramer Bussel," "Rachel Kramer Bussell" and "Rachel Kramer" and...all yield different results! Just something to think about.
And speaking of Seal, check out some of the other books superstar editor Brooke Warner (and yes, she's my editor on Dirty Girls: Erotica for Women, a book Seal inherited when Avalon Publishing closed down Carroll & Graf):
BACHELORETTES, BRIDEZILLAS AND BEAUTIFUL CORPSES: Unraveling Reality TV's Twisted Fairy Tales, by Jennifer Pozner
An expose of the ways that reality television denigrates women.
SUSIE BRIGHT'S MEMOIR by Susie Bright
A first memoir from America's favorite feminist sex expert.
THE STIRRUP QUEEN'S GUIDE TO INFERTILITY: How To Survive in the Land of IF, by Melissa Ford
From the creator of the Stirrup Queens and Sperm Palace Jesters blog, this book provides advice and emotional support to men and women struggling with infertility.
DIRT: Writers on the Gritty Truth of Keeping House, edited by Mindy Lewis
In this anthology, writers reflect on how we make sense of our lives, sort out our messes, and restore order to our psyches through cleaning and keeping house.
CHILDFREE BY CHOICE by Laura Scott
A in-depth examination, including interviews with over 100 women (and some men), about why more and more couples are opting to remain childfree.
THE LIST: 100 Ways to Shake Up Your Life, by Gail Belsky
100 awesome suggestions for women who want to want to do something that adds a little thrill to their lives.
SWEET CHARLOTTE'S SEVENTH MISTAKE, by Cori Crooks
An artistic and poetic account of one woman's search for her real father---with photos, newspaper clippings, and prose.
*But let me just say that in the next few months I truly, truly hope that I can tell you how I turned my cupcake blog into a book. We've had some interest from a very well-respected publisher who I would LOVE to work with, so I'm just putting it out there that I really hope that works out, because it'd be an honor to work with them and their vision is so in sync with my own for a cupcake book. Thank you, universe.