TA Training: General Online Teaching Background
The ACUE Online Toolkit contains a wealth of good advice about getting started teaching an online class. Most of this is based on class design and activities for teachers; however, some of it is also useful for TAs, both in terms of general background about online teaching and TAing, and in terms of specific tips you might find useful in your TA work.
(Also, the site was constructed for Fall 2020; however, most of the information is still useful.)
Your Task
Explore the site. Do not feel obligated to read or view everything on the site. Instead, focus on what you think will be most relevant for you. Then come up with one or two principles, strategies, or activities that will be helpful in your TAing, and write notes for yourself about how you can use those principles, etc. once classes start.