Captions are a great resources that can benefit everyone.
This is a great resource from our friends at Stagetext which has tips, hows to on captions, feedback and best practice checklists. Link is here: http://www.stagetext.org/about-stagetext/digital
Remember not to use autogenerated captions, but create your own which are easy to do. How to subtitle your own content is just here http://www.stagetext.org/about-stagetext/digital/training-in-how-to-subtitle-your-own-content