A few low-effort habits go a long way toward more accessible content:
Use a font size of at least 12px, with sufficient contrast between text and background.
Use proper heading styles in a logical order.
Add alternative descriptions to images that convey their full meaning.
Use tables only for tabular data, and make sure every table has column headers.
Use built-in list functionality instead of manually formatted lists.
Make sure link text describes where the link goes.
Avoid scanned PDFs, and make sure PDFs are tagged.
Ally will flag issues related to these best practices automatically as you create or upload content, and walk you through fixing each one.
For more information, visit Improve Content Accessibility.