Step 1: Becoming XHTML complaint is a logical first step. Becoming XHTML complaint makes pages more compliant with other browsers, and automatically resolves quite a few accessibility options (as noted in the XHTML Checks) You can view the page Why XHTML? for more information.
Step 2: The next logical step is to use an accessibility checking tool to review the web page. The tool that seems to do the best job about informing the user about potential accessibility options is Bobby WorldWide. Quoted from the Bobby WorldWide site: "Bobby was created by CAST to help Web page authors identify and repair significant barriers to access by individuals with disabilities."
Step 3: Even though a page is XHTML complaint and Bobby compliant, it doesn't necessarily make the page Web Accessible. The last step is to check the page against the Manual Checks to make sure that you have meet the compliance requirements.
If you are using the UWP Web Template, you can automatically check any page for compliance by clicking on the Last update date in the footer. It will take you to the W3C's Validation Service. For more information about how to write XHTML, please visit the Resources Links.
To be Bobby compliant, you should strive be Bobby AAA Approved. The page must pass all of the Priority 1,2 and 3 accessibility checkpoints established in W3C Web Content Accessibility Guidelines 1.0. Bobby will notify that there are user checks that need to be done.
The last step is to do the manual checking. Validating tools can't check for everything, so it's important to take the time and check the Manual Checks against your web page.