So trying to have a somewhat normal conversation with an unconventional, off-the-rails personality is something he's navigated before.
Also, Biden almost single-handedly changed the trajectory of the 2012 election with the VP debate. Obama did not do well in the first debate with Romney, and many Democrats were becoming nervous in those days about Obama's re-election. Biden's takedown of Paul Ryan set the campaign back on course.
The best bet is for Joe to just be himself. If he's over-handled, he won't come across right. He is so good at delivering an attack with a smile, easily going into "quiet Joe" voice and then knowing when to bring the fiery rhetoric. As long as he's got his facts straight and knows his stuff well enough to counteract Trump's bullshit on the spot, he will do well.
Speak from the heart, Joe 
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