If you don't have a serious commitment from your StarCraft2 guide to help you understand the unit combinations and how they interact with each other then it's likely you need a new guide. If you do not have access to this type of information within your StarCraft 2 guide then the chances of you mounting a strong game are slim to none. Full game development relies on the ability to combine units and create synergy derived from the races. Knowing which units from which races to combine will be essential as you play. Combining their energies can give you a much more powerful force than either unit could ever be on their own.
The Protoss and Terran races have some highly favored combinations of the own. It's been noted the bringing the zealots and the marauders together has created excellent power and has been a player favorite. In order to win through the earlier games, many players swear that this is the essential combination. Some players report that this combination brings them early game wins in as little as ten minutes. The most favored combination involves about ten marauders and as many as eighteen zealots.
What makes a combination so powerful is how the units are able to operate independently and create a combination in this effect. When each unit effectively compliments the skills of another it works very well. For instance, the marauders are excellent for breaking walls and slowing down the units of your opponent. Zealots are not able to perform this task. The marauders can be used to help the zealots gain entry while holding enemy units so that the zealots can then go forth with an attack. It's simple but it works well almost every time.
You also have to consider the enemy and how well one or both of the units will hold up under attack. The marines, the zerglings, and the stalkers are often very threatening to the marauders but not to the zealots. Thus, the combination increases the strength of marauders against such attackers.
Protoss and Zerg also tend to create some pretty sophisticated and powerful combinations. The roaches and the stalkers are often combined in the earlier games. Stalkers tend to use the roaches very much like tanks and when engaged, the blink ability helps prevent the potential for sustained damage. The roaches are able to burrow and heal while underground and are well armed against the attacks of the zealots, zerglings, and marines. Stalkers are quick to cut down mechanized units of the opponents while also being excellent at avoiding damage from air strikes.
Combinations in the StarCraft 2v2 guide should be explicit and offer up a lot of insight as to why you want to combine particular units. Developing the strength of each unit is the ultimate result. However, if you know which units from which races blend together the best and why they tend to then you will have an upper hand should you see one of the known combinations from your opponent. You certainly want to be able to defend against these units as well as use them in a well formulated attack with the perfect starcraft 2 guide.