Some of the things I look for are:
– Does the tab order make sense and can I reach all controls on the page?
– Is there a clear focus indicator for interactive controls?
– Are there any offscreen elements which should not be focusable?
– Can I traverse the page with a screen reader without getting stuck?
– Is there appropriate alt text on images?
– Do custom controls work with a screen reader?
– Is the user alerted to new content added to the page?
– Are there appropriate headings?
– What about landmark elements?
– Is text high contrast enough to be legible?
And here are some of the tools I like to use:
– Chrome aXe extension: https://goo.gl/67Bm24
– Chrome accessibility devtools extension: https://goo.gl/DvAxi2
– aXe-core: https://github.com/dequelabs/axe-core
Sidenote: at 5:18, not sure why the video didn’t announce the different sizes but I tried again later and it was working. Maybe a VoiceOver quirk.
Watch all A11ycasts episodes: https://goo.gl/06qEUW
Subscribe to the Chrome Developers YouTube channel for updates on new episodes of A11ycasts: http://goo.gl/LLLNvf