Find an inactive base with high level nearly to completely full collectors.
Select your barbarians (use 20-25) and drag your finger across the screen in the area you want them to attack (don't hold your finger down in one spot, this is one mistake people make and that can lead to a mortar destroying all your barbs/archers in one hit).
Put a wave of archers behind them (use 25-30)
Do this same thing on all the sides that have collectors.
Once all collectors on the outside have been destroyed, if you have troops left, then you can go for the ones on the inside. Minions can go over the walls and get these collectors.
After all collectors have been destroyed you can go for the 50%, normally at this point I only have archers and a few barbs and minions left. A king is optional.
(No execution notes)
This raid brings lots of loot for a low training cost and time.