the only right answer is: it depends on your opponent, and it might be partially gambling. Last year I gambled right.
the only obvious thing is: CT in the third game.
:)
Now also a quick reaction to the one asking why anyone would CT in the second game: because it might be your only chance to win the series. Example:
A playes normal against B in B's arena and looses. This means B played either normal, or CT. Next game B will likely play TIE to gain enough enthousiaism for the final game, BUT A is expecting B played CT the first game to certainly win it to be able to TIE the second game and plays TIE as well with a much better enthousiasm, since A only normaaled and did not have a huge drop.
So, A wins the second, and also the third game, due to higher enthousiasm. Should B had CT-ed in the second game as well, he'd probably won the series, where now he is the looser...
I tried to figure out a system last year, and believe me it took me days. In the end I came up with the result that there is no 1 way. Depending on how your opponent chooses his CT and TIEs you will always have a chance of loosing the title... So gamble; stick to your plan, and hope your opponent plays it the way you gambled, if not... well bad luck. Rememeber either he, or you will have bad luck, but someone has got to have it.
They are not your friends; they dispise you. I am the only one you can count on. Trust me.