Make sure you can navigate and operate your page with the keyboard alone.
Include clear and concise ALT attributes for all relevant images and graphics appearing in your site. "Comment out" (for the screen reader) strictly decorative graphics with alt = "". Use a testing tool to view images replaced with their alt text. WebAIM: Images
Tables Data - Use row and column headers to help identify cell contents. In data tables that are nested use the "id" attribute to clarify cell titles. Layout - How a table content "looks" and how it "reads" can be two different things. Use a tool to linearize your table to make sure it still makes sense. This is the order that a screen reader will read it. WebAIM: Tables
Forms Use "label" and "fieldset" attributes. Submit via a "button" rather than an automatic script. WebAIM: Forms