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The most powerful 1-2 punch tennis strategy is a serve followed up with a forehand. You're stacking the strength of the serve with the strength of your forehand. This is the "go to" serve strategy on the pro tour, one that allows them, and will allow you, to hold serve consistently.
The way Novak Djokovic uses it is a little crazy. When he hits a second serve, often he'll aim for his opponent's forehand, instead of playing it safe and aiming for his opponent's backhand. In the deuce court, that allows him to pull his opponent off the court and force them to hit a running backhand as their next shot. In the ad court, it's more of a changeup, he doesn't use it quite as often, but it's still incredibly effective.
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Here's the link one more time - bit.ly/46BtgCP