Never speak if lights are out for example when using slides or video. Never shout instructions or information from a distance. Try not to show impatience if you must repeat information. Try not to be dismissive rather than repeat information. Easier to avoid is the complaint that TV or video programmes without sub-titles were used as teaching materials.
Support is important especially at the beginning.
Several students drew an interesting distinction between goodwill, which they felt was generally there, and awareness of the issues, which was less clear.