Myth #1: SEO is all about secret tactics
I talk to a lot of people about SEO, plenty of whom are new to it. I'd say the most common myth is that SEO involves all "secret" tactics requiring you to buy links or trick the search engines, and that no one in the industry can be trusted.
In reality, there are a lot of simple but effective techniques that even the search engines will tell you to do that can increase traffic. And there are plenty of people who are not snake oil salespeople who can provide this useful service. A good place to start the process is to look at your analytics. There are a variety of tools, including some from Google, that spotlight if you have problems being accessed by search engines. I also like a top-down approach. You start from the homepage and ensure that it is search engine friendly, then work your way back through the site going down the paths that are most important to your business.
This is completely spot on... just like any successful marketing campaign, there are certain basics that if executed properly can help you achieve your desired results. There are lots of valid tools out there to help you - Google analytics, Google webmaster tool, SEO Elite, and others.
Make sure you have the right tools to evaluate the current state of your site and direct towards which actions to take. This ensures that what you're doing will generate a return and improve organic search results.