The One Click Accessibility plugin handles a lot of the basics of meeting accessibility standards as well as providing a front end widget for visitors to adjust the page to meet their needs.
It is best to get in the habit of adding Alt Text to an image during the upload process. Alt Text is used by screen readers to provide a description of the image to those who can not see it.
When the color of text against the color of the background does not have sufficient contrast, many people are unable to easily read it. What may look aesthetically pleasing to you may be unreadable to a visitor. While the minimum recommended ratio is 3:1, we would like to aim for at least a 7:1. There are tools out there to help with this, one for OSX users is “Colour Contrast Analyzer”.
The lighthouse feature in chrome, or googles page speed insights application, will provide good feedback on a page’s accessibility issues.
Performance and Responsiveness
This will be expanded on in a separate section, but performance is an accessibility issue. Some visitors may only be able to access your site from very slow networks, or only from certain kinds of devices. If your site takes too long (or fails) to load on those networks, or does not look or perform correctly on those devices, then those visitors are being excluded.
Using plugins and automated tools for addressing accessibility is an excellent start and will do most of the work. However, they can not account for all needs. Listen to feedback from the populace and make adjustments accordingly. If someone tells you they have trouble reading text, their screen reader gets stuck on a given page, they can’t get to the information they need on the device they rely on, or any other kind of issue: Believe them and work to fix it.