If I were Biden's counsel:
Present with command and calmness. Answer the questions as if you are the President.
The jury is the TV audience. Speak to them. Steady tone. Be yourself. Be conversational.
Treat Trump with irrelevance. Do not show any respect for him, only his office.
Do not get sucked into the muck of countering Trump's repeated lies. Stay at a higher elevation. Look at him and say things like, "Good news Donald, ... you are not under oath" or "It must be convenient going through life without a conscience"
When you face or speak towards Trump, use a firm scolding type tone (parent to child). When speaking to the TV audience, use a respectful and forthright tone.
Link: https://www.nytimes.com/2020/09/27/opinion/trump-debates-2020.html