This is worth your time. It’s a talk by Monika Piotrowicz of Shopify. I like her instruction to use basic HTML whenever possible instead of putting something else in to overrule the semantics. Her explanation of ARIA is excellent.
The close captions aren’t great. They were generated automatically rather than from a transcript, but they do appear if you need them.
Hat tip to Dennis Lembree who shared this on Google+, which is where I first saw it.