Several rules about the beginning of the game must be followed: At the very start of the game you have 4 harvester units. Most people group all 4 of them and send them to 1 mineral to have them harvest, but there is a problem with this. There will only be 1 unit harvesting the mineral that the player clicked on, and the other 3 will wait. To gain a few seconds right off the bat in the beginning of the game, have them all walk towards one mineral and one by one pick them off, sending them to separate minerals. When you have a unit training (an SCV, probe, marine, zealot etc.) Never have more than one on the list until they are about to finish. IF you have two on the list ready to train, you may not be able to build a building or train a unit that actually needs to be trained. When you put extra units on the list, it takes away from the units you currently have, depriving you of minerals you need early in the game to build essential buildings. For example, the first barracks finishes. You start training 3 marines in there, which spends away all of your money. You have to wait about 15 seconds before the SCV starts to build the bunker, and so the enemy zergling rusher comes in and kills the marines who would have been in a bunker otherwise. It's not a good situation… Sure you have another marine coming out of the bunker but what's he going to do against 6 zerglings? You can have both the bunker and the other marine coming quickly enough to fend off any rush. Never allow a harvester unit to be idle. Even if you're waiting to get enough minerals to build something, you would be better off if that unit was harvesting and you picked one out later to build the building. Remember to do everything as quickly as possible. Every second you waste or gain adds up with the other seconds you wasted or gained. You can see how well you're doing in the beginning by comparing your statistics with other players if you quit a game before anyone attacks. Generally, you stop building harvester units when you have almost 2 for each mineral you are harvesting, 3 for each vespene geyser, and 1 for each building you're making (for terran and zerg.) Note that these build orders are not perfect, no build order can be perfect, but these are extremely good and should work with and against almost any strategy.