Duane Forrester, who runs the in-house SEO program for the MSN properties in Canada, the US and The Americas gave some great SEO advice in a post on Search Engine Land:

• Rankings are NOT metrics
• SEO should be baked in, not spread on top
• SEO is a game of inches, not miles—there’s no ONE thing that will make you a hero
• Usability trumps SEO—the user’s experience should always be the # 1 focus