Building placement is a fundamental skill that separates average players from masters. The Cannon and Tesla are core defensive staples; the Tesla is particularly valuable as it hides underground, making it immune to spells until triggered. For high-health tanks like the Golem or Pekka, the Inferno Tower is essential for its ramp-up damage, while the Bomb Tower provides crucial splash damage against swarms. If you need a reactive defense that turns into an offensive counter-push, the Goblin Cage is the premier choice, releasing a powerful Brawler once the cage is destroyed.
The most critical technique is the 'Building Pull.' By placing a building in the center of your map (the "kill zone"), you force building-targeting troops like the Hog Rider or Giant to deviate from their path toward your Princess Tower. The optimal placement is usually 4-5 tiles from the river and 1-2 tiles into the opposite lane of the attacking troop. This maximizes the distance the enemy must travel while ensuring both of your Princess Towers can fire on the target simultaneously, doubling your defensive DPS.