Trump is good at needling people. He just needs to find the best way to get under Joe’s skin without looking mean. He needs to be calm and let Joe be the one to lose his temper.
The only people Trump needs to be combative with is the moderators when they jump in to try and save Biden. If Slow Joe shows up, Trump doesn’t want to come across looking like a bully. He just needs to point out Biden’s policy failures and, in an almost pitying way, point out that he’s not mentally or physically fit to hold the office of the Presidency.
If Jacked Joe shows up, Trump needs to stand up to him not so much that undecideds walk away saying “They’re both unhinged jerks”. People need to walk away from the debate with a clear impression that Biden was the one who was combative, not Trump.