In small battles, especially early in the game, you should use these simple tactics to put yourself at an advantage. If you are using range units such as hydralisks or marines, use waypoints when killing your enemies. If there aren't many enemies compared to your units, it doesn't matter, and if the battle is too large (over 12 units on your side) it really won't make much of a difference. Hold shift and hit and then click on an enemy, doing this as many times as possible. With zealots (and this really only works with zealots, possibly with fast air units) you can win a battle of equal proportions using the following tactic. When the zealots get into a fight with against other zealots or zerglings, watch their hitpoints drop. When one zealot's shields die out, and it begins to take hits on its armor, click on it and walk away from the battle a short distance so the enemies target the other zealots that have more hitpoints. Then have it go back to the battle, and do damage while it is not targeted. Often you will not have enough time to do these things, especially if you are trying to build up and you have several expansions. If you have enough time to spend away from building your base, it is important that you use these tactics to destroy the enemy or defend yourself