Find a base with many buildings outside of the walls.
"Test" the defences with Archers, as they have a longer range than Giants or Goblins. You want to "pick off" as many buildings as you can without wasting all of your troops. Alternatively, you can use Minions if you have them. You can place your Minions in range of Cannons and Mortars, but if you are using them, take out their Air Defense first.
You can then "distract" their defences with the Giants by breaking into their "pockets" with the defences in it. You can place about 2 Giants at a time while you send in the Goblins or Barbarians depending on what buildings are in that "pocket".
After a breaking into a few "pockets" you should be at 50%. It is up to you whether or not to continue the attack.