1) Buy (or Sell) Links. OK, this one is tricky. If Google catches you buying links, you’re sunk. But couldn’t you just do it all sneaky so Google doesn’t notice? Probably, but keep in mind Google still hates it and will blast your site if they find out you’re doing it.
SOLUTION: Create awesome and compelling content so that people link to you naturally for free. It works, but it’s easier said than done.
2) Free Giveaways/Promotions. That’s right – Google will also penalize you for asking other blogs to link to you in a free promotion or giveaway. In their eyes it’s just like buying links. I’ve done it, and I’ve seen it.
SOLUTION: Ask any blogger doing a promotion or giveaway for you to nofollow their links.
A former Google Quality Rater writes “If you publish a product review or giveaway and you don’t no-follow your links, Google will penalize both you and the company that sponsored your blog post.”
3) Uncloaked Affiliate links. Why does Google hate affiliates? It seems Google hates just about anything commercial – if it makes you money, Google doesn’t like it. Unless of course you’re paying Google, as in buying Adwords for PPC. Then they love you. Not cloacking your affiliate links can cost you in the SERPs. I’ve done it, and I’ve seen it.
SOLUTION: Cloak the links — 301 redirects work great — and nofollow them.
4) Linking to Spammy and Shady Sites. Watch those commenters you allow to place dofollow comments on your blog – if you get enough people linking to sites which sell Viagra and pr0n via hacked links you’ll get slammed for linking out to bad neighborhoods.
SOLUTION: Moderate your comments, nofollow links, or both. Others more experienced than I have blogged about it.
5) Inactivity. The search engine landscape is changing all the time – if you’re not constantly working on promoting or building your site chances are it’s going to slip in the SERPs. You can’t just put up a 5 page brochure/pamphlet site and expect visitors to find you. You have to work at it.
SOLUTION: Work at it.
6) Duplicate Content. OK, this one won’t destroy your site, but it’s not going to help it any. If your site suffers from internal duplicate content issues search engines may not be returning the pages you want visitors to see. If your site has duplicate issues with content previously published on other websites, you may not appear at all.
SOLUTION: Nofollow links to duplicate content, block it in robots.txt, and/or use the new Google Canonical tag to specify the authoritative source.