The most common accessibility fixes you can easily take care of are:
Alternate text for images
You can insert an image in Word documents or Outlook email but, if you take care of adding alternate text, you have an accessible document or email that may be read by screen readers. Watch the tutorials.
You can use colors that you know are readable and have high contrast so they are visible to most, if not all, users.
Self-Explanatory Link Text
You can include links that are self explanatory instead of long urls that are painstakingly read by screen readers or do not necessarily indicate where they link to.
You can create forms that are usable and accessible by having fields that are clearly labeled and including clear instructions.
Readable and Understandable Tables
You can make usable and accessible tables that have clear headers and no complicated formats like merged cells.
By including accurate captions, you appeal not only to persons who are deaf or heard of hearing but to those mobile users in noisy environments, English-as-a-second-language speakers, and many other users.
You can check your documents using the accessibility checker included in Word, PowerPoint, and many other frequently used applications.