A couple of years ago, I bought an ad on a blog, and I noticed an uptick in DVD sales.

In the time between then and now, there's all sorts of concerns about hardlinks and such, and Google ranking.

My biggest traffic generator is Twitter. Followed by FaceBook.

What are the things to look out for these days, with buying ads, links, pop ups, pop unders, etc, as each affects SEO?

Which are the best to try? Other than Twitter and FaceBooks?