” … people might not be able to tell the difference.”
Also, of course, he should address and refer to her always as “Governor,” or “Governor Palin,” and neither condescend nor say anything mean. Even attacking McCain, usually the VP candidate’s job, might not be a good idea, since that would give Palin a chance to play the loyal subordinate defending her boss.
Biden’s strategy should be the same as Obama’s, only more so. His job is to stand on that stage and look like a President, while letting his opponent look like … something else. And remind the voters which ticket is proposing policies that work for working people.