Accessibility Training – accessibility @ perpendicular angel design

The following articles and videos will help you understand the basics. Many of them cover the same material from different angles or levels of depth.

Accessibility 101

The Web Accessibility Basics by Marco Zehe on Marco’s Accessibility Blog.
Getting Started with Web Accessibility by Monika Piotrowicz at The Pastry Box.
Dos and don’ts on designing for accessibility by Karwai Pun on Gov.UK.
Designing for Inclusivity: How and Why to Get Started by Allison Shaw at the Invision Design Blog.
Exclusive Design by Vasilis van Gemert is a thesis describing what design would be like if we designed not inclusively, but exclusively for people with disabilities. It’s a long read, but covers a lot of ground about our current assumptions.
Mythbuster’s Guide to Accessibility by the US Digital Service puts a governmental lens on accessibility.
14 easy ways to make your website more accessible by Carl Cahill and Joss Cook.
Common Accessibility Mistakes and How To Avoid Them by Ben Robertson outlines four of his own principles for developing accessible websites.

Read Can you reach anything that’s interactive using the tab key? to learn how to navigate a website with only your keyboard.
Read Can you use a screen reader to access the page content? to learn how people with screen readers use the web (and how you can learn if required).

Online Self-Paced Web Accessibility Classes by Deque – These include training classes specific to various roles as well as the full curriculum for IAAP certification preparation

Extreme Design by Derek Featherstone at An Event Apart explains how designing for accessibility needs helps us think of extreme scenarios that result in a better design for everyone.

Accessibility Support site -indicates accessibility support built in for various components.
Paint the Picture, Not the Frame: How Browsers Provide Everything Users Need by Eric Bailey on A List Apart outlines some major browser functionality that is sometimes recreated by developers, such as a scroll-to-top pattern, scrollbar designs, scrolling, highlighting, text resizing, high-contrast themes, moving the focus, the clipboard, and browser history, that really probably shouldn’t be messed with unless you’re going to be incredibly thorough and consider a wide array of inclusive use cases.

I think the best accessibility checklist is the one you make yourself, but these might get you started.