Avoid Neighborhood Kids - Accidentally tapping these otherwise healthy children will instantly end the current game.
Don't wait for the zombies to reach the middle of the screen. Smash them as soon as possible.
Tap Zombies In Rapid Succession - This helps build a combo that in turn will move you one-step closer to achieving three stars for that particular stage in Story mode.
You receive three hearts in Story mode and lose one each time a zombie disappears off screen. Always a good idea to know how many you have left.
Power-Up strategy
You only have a limited number of these items at the beginning and acquiring more means having to spend money. Utilize the Meat Lure (attracts zombies), Lightning (fries them) and Bomb (blows those suckers up) at your most desperate moments. Example: being overrun by swarms of enemies.