By structuring your word documents well, you will help people using screen readers navigate your document more easily. Additional benefit: your document will be more visually appealing and you can automatically generate a table of contents.
Use the Styles feature in Word (Title, Heading 1 for top level info, Heading 2 for subheadings) rather than structuring your document manually (using bold, different fonts and sizes, etc.).
For images, charts and graphs, provide a brief description using alternate (alt) text.