I joined Twitter several years ago, largely for promotional purposes, but while I've since amassed a respectable list of legitimate followers, I haven't successfully made much functional use of the account. I mainly use it for personal expression, and while I occasionally link to some of my online publications, I'm not sure how many people those posts actually reach.
I am working on a new novel, and I know that some people have successfully built an advance fanbase for their work through Twitter and/or other social media. Are there good guidelines for doing this successfully? I've seen some other writers on Twitter post what amounts to a writer's diary, but I'm not sure how compelling people actually find that approach. I've also thought about commissioning and publishing character sketches, but that can quickly get expensive, and might be premature. I've also thought about publishing excerpts, but I worry about copyright issues, and what prospective publishers would think.
Realistically, I'm probably at least a year away from completing the book (let alone selling it). However, it seems like starting early and building steadily is a more productive social media strategy than doing a sudden late push.