Problem: Too old. Solution: Do whatever you have to do to appear fresh and alert any time you appear in public. If that means limiting personal appearances, so be it. Remember, Reagan took a lot of naps.
Problem: McSame. Solution: This is an easy one: bring back McCain the Maverick. Put as much distance as you can between yourself and Bush, any time your conscience allows. Pull the rug out from under Obama whenever you can. You don't really care about domestic issues anyway: how about a healthcare plan that's to the left of his?
Problem: Temper tantrums. Solution: Actually, that's one of the things people like about you, if you do it right. Pick your targets carefully and then hit them with humor/righteous outrage.
Problem: Gaffes. Solution: Why is this a problem? It's not as if American voters refuse to vote for candidates who couldn't pass a 6th-grade geography exam: see W. Bush, Reagan. And anyway, it's a great counter-image to Smartypants Obama. Just remember to show self-deprecating humor when your booboos are pointed out.
Problem: Conservatives hate you. Solution: So what? It's not like they're going to vote for Obama. If you lose because a tiny minority of hardliners stays home on election day, you were never going to win anyway.