When there is water in front of you or blocking your path, only you can walk through it. If your goblin minions go out of the shallow end of the water they will drown, and can only be saved by blue goblins. Instead of guiding your goblin minions across a complex path to keep out of the water (which they usually fall in anyway and drown), simply walk through the water. Your minions are smart enough not to follow you and will automatically seek the easiest path to get back to you. Be careful; sometimes your minions cannot get through because a bridge needs to be activated (for example, Blue Goblin Cave).
Always have blue minions on guard duty. While on a guard post, they will actively run into the combat, grab a fallen peer, and drag their half conscious form over to you so they can revive their fallen comrade. However, while not assigned, they will wait for you to micromanage them over to the body by sweeping, making them almost useless in a large battle.
Easy soul gathering:
In order to do this you must have fought Dazzler Beetles (found in the blue minion cave), Puff Beetles (Evernight), Magma Beetles (outside of Heavens Peak) and Battler Beetles. After you have fought at least one of each, they will be available at your dungeon. Go to your dungeon and choose to fight one of the four. The easiest way to take out the horde of beetles is to pull only a few from the swarm and take your time killing them individually. Green minions work well due to the fact that they are experts at overwhelming and killing your enemies. Set a marker for them to wait at and they will eventually turn invisible. Pull a few beetles and make them follow you to the marker, where your minions will then jump on them and eventually kill them. Battler Beetles are good for getting Brown souls. Puff Beetles are good for getting Green souls. Magma Beetles give red souls and Dazzler beetles give blue souls. You should get at least 75 souls each time you completely kill all of the beetles that are in the dungeon.