Public Interest

I've been watching this thread! Sorry I probably won't be TOO much help because I haven't published the first in the series yet- but as a reader I think that a blurb as soon as you know the sequel is always welcomed by a waiting fan.
Snippets are always good too. Although I've only done one on my blog for the first book so far. : ) I think it just depends on the author!

I would recommend that you post updates about the new book, with quotes and background information once a week or at least a couple of times a month. Do you have a newsletter list on your site? Posts that go directly to your newsletter subscribers will keep them engaged and interested leading up to your next release.

Pop some short stories up, or background related to book 1 and book 2. Talk about where you write. Ask your fans for comments about anything related to the books.

It's all about engagement. Only posting when you have a finished product will make for a boring site and you could lose your fans interest.

I wouldn't honestly say to start posting about the second book when you at the very least have a first draft of it. My reasons are basically, if you get people excited about something and then, for whatever reason, never finish the book and it never comes out, readers are going to be disappointed and you run the risk of, next time you are publicising an upcoming book, there won't be so much interest in it because you haven't finished this one.

Also, I would give readers a little time to read the book, review it, recommend it etc, talk about it, before you start to bombard them with things for the next book.

So, if you are planning on having a first draft finished in May and the book out in August, then I would say start to do the promo for it at the end of May, start of June.

Now, I know this only leaves you a couple of months, but people have short attention spans and if publicise too far in advance they either forget, or get annoyed at too much publicity.

Just my two cents.