This attack strategy works best on TH6s and new TH7s. You will need a Barbarian King.
Use the Lightning Spells to destroy any mortars. Try to get a Wizard Tower or another ground-offensive tower.
If you accidentally lure out Clan Castle troops, simply spam archers in a semicircle around them. If there is a Valkyrie present, spread archers around even more. Use the third lightning spell on them if desired.
Drop all 4 wall breakers into the side with the destroyed Mortar(s). 4 of them will make sure at least 1 get to the wall.
Use Archers to pick off and snipe gold mines, elixir collectors, and other buildings outside the walls. If there is an exposed Town Hall, be prepared with hordes of Barbarians to take the Teslas out, but disarm the traps first with one or two troops. Don't forget to take out builder huts in the corners of the maps if there are any.
Once your troops have made their way into a wall pocket, use spread-out archers to destroy any remaining splash-damage towers. On the other side of the base, drop a Barbarian King along with a few barbarians for backup. He will ensure you get at least 50%.
If your troops get stuck on a wall and there is a mortar firing at them, remember to keep backup troops (Clan castle troops, preferably an air troop like balloons or a dragon.)
This strategy is guaranteed to get at least 50% on any TH6 base.