Step 3 - Review Your Internal Links
Next you'll want to review you internal linking structure. The first step in reviewing your linking structure is to make sure you have no broken links within your website. This can be done in many different ways. Hopefully you've already arranged to have an automated link checker, but if you haven't you can find software and services that can do this for you on a one-off basis. Having broken links is not only a waste from a search engine optimization perspective, but it's also detrimental to your website's audience.
Once that bit of housekeeping is taken care of, then you need to start looking at your link text. Fix up as many "Click Here" or "Download" links as you can. Use descriptive link text because they weigh heavily when it comes to search engine optimization.
Finally, make sure that your link structure includes all of your pages. You don't want to leave any out. Throughout the entire link review process, look for linking opportunities within the content of your pages. Menu links are important, but links embedded within content are significant. Use this to your advantage.
Step 4 - Accessibility and Validation
The next task you'll want to undertake is to make all of your web pages validate to HTML standards and make them at least minimally accessible. Some will argue that this isn't "necessary" and they're right. This isn't a necessary step, but it's one that will save you work, grief and help your website reach as broad an audience as possible.
Maintaining valid code will produce more predictable end results. If you're using a content management system, deploying a standards compliant template to the entire site can simplify the task. This task can be simplified further still if you have an automated system in place to check your site for validation problems. Don't you wish you'd automated some of this stuff back in step 2? :)