Every game of Starcraft takes place on a unique galaxy layout. Not only does this add diversity to the game play, but it introduces an additional of level of strategy. If you approach this portion of the game in a some what random approach, you can find yourself playing one large losing battle. Prior to placing any planets down, start by deciding which planet you hold will make the best home planet. Then arrange the planets in such a way to give your forces the most amount of resources and deny your opponent the same resources. Let us examine each of those points in detail.
I wish that I could rank the planets from most desirable to least desirable in terms of home planet, but it is just not that simple. It really depends on two factors: what faction you chose and what victory condition route you are taking. Acturus Mensk, might want to go for the smaller of the two planets and prepare for a defensive battle. The Queen of Blades and Aldaris might want to go for the planet with the most control points. Tassadar wants the largest planet possible. Raynor's dream might would be to pull Dylar IV, Pridewater, or Torus where as Abaddon is the equivalent to suicide in terms of special victory condition. The Overmind may be the only agnostic faction when it comes to home planet and special victory condition. Of course, that line of thinking assumes that you want to go for special victory. If you plan to go for a standard victory, just go for the planet with the most control points. Which ever you choose, plan your your strategy from start and do not try for a late game strategy change. Trying to change your overall goal of the game can be catastrophic.
The overall objective of planetary placement is to put you in the best position and to put your opponent in the worst position. Sounds easy right? No, not exactly, especially with the addition of the z-axis navigation routes. That doesn't mean you shouldn't try. There are two rules that every player must follow. The first is do not let your home planet be the first planet on the board. If you do this, then you are just asking to get boxed in and the game will be an uphill battle(both ways and through the snow) throughout the entire game. Always place your home planet such that there is at least one other planet adjacent to it which contains no enemy forces. Preferably, find a place with two adjacent neutral planets, but having one other planet is a must. Why it is awful to find yourself boxed in by your opponents, it just plain incompetence to box yourself in. The last thing to consider is align the planet in such a way that it uses as many of its connections as possible. Since the Z-Axis navigation routes come last, it is much better to know where your planet is connected to instead of leaving it up to chance later.
Let us take a look at a few of these ideas in practice. Just for the record, all the pictures I am using are from a large scale battle we played with some special rules, but the planet layout tactics remain unchanged. Also, each of the three players(Zerg,Terran, and Protoss) started with two bases.
Start with the top image. Here is why you should make sure that as many of your connections are used before the placement of the Z-axis routes. Antiga Prime was one of the Terran home planets, but the Zerg and Protoss Players placed their Z-axis routes attached to the planet. In the end, the Terran forces fought a defensive battle with the planet nearly being overrun.
Now examine the middle picture. The planets boxed in blue were the two Terran home planets and the planets boxed in Orange were the two home planets for the Protoss. The various z-axis routes attached to these planets only went to other enemy home planets and not any empty planets. Between these two players, there was only one empty planet adjacent to their four starting planets. This game featured nine planets in the galaxy. (The other four being off to the left and they were captured by the Zerg with out any fighting.) This is certainly a tactical gamble on the part of both players. The outcome of the war between them would come down to who controlled the fifth planet. In some situations this decision could be a valid tactical decision, but in a game with so many planets, it was really a mistake. There is no reason one player should be able to control almost 50% of the galaxy with out a single battle. The bottom line is, if you choose to go with this style of setup, expand to the contested planet as soon as possible so that your enemy does not control it. Neither player made any advances to this planet until late in the game. Though in defense of the Terran player, he did have his hands full as the Zerg spent the entire game harassing Antiga Prime.
Now we come to the Zerg setup which happens to be the setup you want to aim for. The third image contains the Tactically Enhanced Image. The green box indicates the two Zerg Home planets. The home planet on the left was placed first and the home planet on the right came later. The two bottom planets, along with Pridewater off to the right of the bottom were all placed before the first home planet. The Zerg player could not have asked for a better setup. He had access to three planets which contained no enemy home bases and two of them would not have adjacent enemy home planets. And if the enemy wanted to get at these planets, they would have to go through other Zerg planets first. The lesson here is to keep on the lookout for “Me-Only” planets and build your empire around them. Holding a “Me-Only” planet is devastating, especially if you are taking the fight to the enemy in the process.
Hopefully, this article gives you some idea about what setups you want to look for to ensure victory for your faction.