Is it advisable to use social networking for book promotions?

Yes and No. Social Networking sites are a great way to reach a lot of people but it depends how you present yourself on such sites. If you want to spend the time actually networking with people and building relationships, then you can use it to promote your work. If you're just going to show up and say, "Read my book 'cos I wrote it and it's great," you'll probably tick off a whole lot of people and do your sales more harm than good.

I think if you've already established yourself on (for example) Facebook and have been telling folks about your progress, much in the way anyone shares their news, then you can simply include a bit of promotion. But if you join a place like that and do nothing more than promote your book, then you will (rightfully) be seen as a spammer.

Sure--just don't exploit the community. Don't make it all about you/your book all the time.

Give back. Pay it forward.

Absolutely. I have my personal Facebook page and my professional one. When I have a book release, my professional page can send updates to people who have signed up to be my 'fans' on the Facebook application page. Occasionally, I send out notices on my personal page about the professional page--that way who want my professional information can be targeted for marketing and the ones who don't, won't be. The key to social networking sites and promotion, just like everywhere else, is courtesy first of all.

If you do it well, it goes well. If you do it badly you make you and your book look bad.