In SEO there are a few techniques that have been flagged that need to avoided at all costs. These are all techniques that used to be perfectly acceptable but are now taboo. Number 1: Spammy guest blogging: Blowing up a page with guest comments is no longer a benefit. Number 2: Optimized Anchors: These have become counterproductive, instead use safe anchors. Number 3: Low Quality Links: Often sites will be flooded with hyperlinks that take you to low quality Q&A sites, don’t do this. Number 4: Keyword Heavy Content: Try and avoid too many of these, use longer well written sections more liberally. Number 5: Link-Back Overuse: Back links can be a great way to redirect to your site but over saturation will make people feel trapped
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Google has the best tools for webmasters, but remember that they aren’t the only search engine around. You should also look into Bing and Yahoo!’s webmaster tool offerings (here are the tools for Bing; here for Yahoo). Both of them also accept sitemap.xml files, so if you’re going to make one for Google, then you may as well submit it elsewhere as well.
Google Analytics is very useful for helping you tweak this sort of thing. It makes it easy to see the effect that your changes are having.
Google and Bing both have very useful SEO blogs. Here is Google’s. Here is Bing’s. Read through them–they have a lot of useful information.
Meta keywords and meta descriptions may or may not be useful these days. I don’t see the harm in including them if they are applicable.
If your page might be reached by more than one URL (i.e., http://www.mysite.com/default.aspx versus mysite.com/default.aspx versus http://www.mysite.com/), then be aware that that sort of thing sometimes confuses search engines, and they may penalize you for what they perceive as duplicated content. Use the link rel=”canoncial” element to help avoid this problem.
Adjust your site’s layout so that the main content comes as early as possible in the HTML source.
Understand and utilize your robots.txt and meta robots tags.
When you register your domain name, go ahead and claim it for as long of a period of time as you can. If your domain name registration is set to expire ten years from now rather than one year from now, search engines will take you more seriously.
As you probably know already, having other reputable sites that link to your site is a good thing (as long as those links are legitimate).
I’m sure there are many more tips as well. Good luck!