General Strategies and Tactics

Ideal Build Order
When dealing with a cunning human opponent, the order in which you construct your first few buildings is literally the difference between potential victory and ignoble defeat. The general rule is to begin harvesting minerals immediately while building more gatherer units, then using your seventh gatherer to build your first support structure (Terran Supply Depot, Zerg Overlord, or Protoss Pylon). Build around two more gatherers thereafter, then set up your low-level unit production structure (Terran Barracks, Zerg Spawning Pool, or Protoss Gateway). As soon as possible, begin production of one or two low-level attackers made available from that structure. More gatherers and one more support structure later, then and only then should you even consider building a Vespene Gas mine (Terran Refinery, Zerg Extractor, or Protoss Assimilator). The rule is to set up a defensive position using only minerals as quickly as possible and only starting to mine gas thereafter.

A second Gateway warps in and another Zealot nears completion, while plenty of Probes gather minerals at this rapidly developing Protoss headquarters.

Building up your base in this fashion lets you either mount a preemptive attack against the enemy early on (a strategy not so affectionately referred to as a rush) or successfully defend against one should you find yourself on the receiving end. An opponent who builds a Refinery-equivalent early on or begins researching upgrades early on is using up resources he could otherwise be spending on bolstering his garrison. And early in a battle, should your forces outnumber the opponent's, your victory is certain. So the rule is to produce several low-level fighters with haste, while continuing to produce gatherer units until you hold a ratio of two gatherers per one mineral patch.

War Is Not for Pacifists
You will find that any given battle tends to favor the aggressor, at least when dealing with a human opponent. Certain types of commanders enjoy wallowing in paranoia and fortifying their positions with as many defensive structures as they can afford, rather than spending that same money on mobile forces. Such opponents are easily defeated, as the Terrans, Zerg, and Protoss all have units designed to eliminate defensive structures from afar.

This heavily fortified Terran headquarters is properly protected by combinations of mobile forces, rather than cluttered immovable defenses.

While all this is not to suggest that defending your headquarters is not important, you must understand that attacking tends to yield superior results than defending. Key structures are easily razed by comparatively small groups of units, and if you insist on always fighting on your own territory, it is likely but a matter of time before your defenses are overrun and your headquarters promptly destroyed.

Know the units that are ideal for building sieges against heavily fortified bases. These include the Terran Battlecruiser and Arclite Siege Tank, the Zerg Guardian and Defiler, and the Protoss Reaver and Carrier. All these units can smash or heavily damage defensive emplacements with little problem.

Next: The Necessity of Expansion and Bypassing Restrictions