Quick dropping is the act when you want to place down troops really quickly. It is ideal for making huge pushes and defense. To quick drop, select the card you want to place down with one finger and hover over the place you want to place that card, and with the other finger, hover over the card you want to select next. Since you want to place them both in about the same area, tap the pre-selected troop onto the battlefield, and in quick succession press the card you were hovering over with the other finger and place it in the same area. Since you already have your finger in the same spot when you placed the first troop, just tap it in the same spot. For example, if you only have minions and zap to counter the baby dragon, quick-drop the zap, then quick drop minions onto the baby dragon. This is a good way to defend against other troops too. You can also read my zap article for more info.