It isn't always possible to tell at a glance if a resource you would like to use in your course is accessible. To start, it is helpful to think about accessibility as a sliding scale (more accessible to less accessible) rather than discrete binary states. There are tools you can use on certain types of documents and resources to help assess accessibility, and things you can look for that will tell you that a deeper look at the resource is needed.
With video content, use the following tips to evaluate potential video choices:
The above is far from an exhaustive list. For more information, please see the additional information provided here and/or contact your accessibility department (Campus Accessibility Center or Online Accessibility Center) or your Library Liaison.