Attacking in waves, is a tactic used to damage more targets using catapults.
With the highest level rally point, it is possible to target two buildings or fields, but to do more, such as taking out the entire wheat production, it is necessary to send several waves of attack, each containing sufficient catapults.
The well tried wave tactic, consists of a clearing wave with the majority of accompanying troops, plus several following waves of catapults with limited escorting force. Since some players may try to dodge the clearing wave and land defence ahead of the smaller waves, a counter tactic is to make the first wave a fake, and the second wave the clearer. It is also useful to make the waves as close together as possible, by preparing them in multiple windows and then giving each one the go as quickly as possible.
It is more difficult to sequence waves from different starting points, though obviously, the furthest/slowest must be sent first, with an eye on the times that closer waves need to be sent.
Do not begin to catapult wave a target unless you intend to destroy or cripple (wheat-kill) the village, and have sufficient strength to resist revenge attacks from the owner's other villages and allies.