How can I even start checking for this accessibility stuff?

I got a question from a coworker a few weeks ago. They received feedback that a screen reader user was having trouble navigating one of the pages on our site. They asked if I could advise on any issues that they weren't able to figure out, and then they asked something like this:

We aren't sure how to test these updates on our own. Are there any tools you could share with us?

I arrived at a simple single answer, but I'll take the long road there.

Automated accessibility tools

I started with automated tools:

Automated accessibility tools can be useful, but they can only find 10-20% of issues. With that being said, one of the better ones that I’ve found is WAVE Evaluation Tool, which is available as a browser extension (I use it in Firefox, but I’ve also used it in Chrome).

This actual percentage varies depending on what source you're looking at, but the consensus is that while automated tools can find some issues, they aren't a good thing to rely on.

Learning to use a screen reader

I continued:

As far as testing your updates on your own, you can check out NVDA for Windows (free), or VoiceOver on Mac (also free, and should come preinstalled).

Screen reader testing is invaluable for testing websites for accessibility, because in the same way that websites will show up differently in different browsers, web pages can be presented differently with different screen reader/browser combinations.

The learning curve is fairly steep if you haven't used any of this software before. Different users navigate pages different ways with screen readers: some prefer to navigate by heading, some by landmark region, etc. I diverted a bit here and suggested a different route.

The "one thing" that you can do to start diving into accessibility testing

Try navigating your pages only using your keyboard.

Learning screen reader software can be a bit tricky, so an easier step that you can do that will also expose some of the same issues is navigating using just your keyboard.

Most screen reader users will also be keyboard users, so finding any issues that exist with your pages when navigating with only a keyboard will also expose issues that screen reader users will run into.

The keyboard shortcuts that you learn by navigating a page without a mouse will come in handy when you eventually start testing with a screen reader.

To prevent temptation, you could even download a browser extension that hides your mouse cursor.