Regardless of what your build order is, or what units you prefer to use in combat tactics, Hatcheries are an essential element of most, if not all, successful Zerg strategies. The Zerg are an interesting race to play and are certainly one of the more unique real-time strategy races. Here are some basic Starcraft 2 Hatchery tactics.
The Hatchery enables the Spawning Pool and Evolution Chamber to be created. Once upgraded to a Lair the Burrow, Pneumatized Carapace and Ventral Sacs upgrades can also be researched. The Hatchery still allows for resources to be dropped off even when upgraded.
Hatchery tactics can vary; it's crucial to realize the importance of Hatcheries first. First-off, they can be expensive to produce and also require a large amount of minerals to produce. They function as a drop off point for resources being harvested by Drones and are also very important as they will allow for the production of more units.
Therefore, the importance of Hatcheries lies in their ability to spawn more units, and with the Zerg there is certainly strength within numbers. No other Zerg buildings can function as resources drop off points.
You should expand when it is logical to do so. Build Hatcheries next to resources and spawn more drones initially to capitalize on the extra resources. Players may often build an additional Hatchery next to an existing Hatchery. This new Hatchery is known as a Macro Hatchery as it is primarly used to augment Zerg unit production rather than act as a resource drop off point.
Creating a small group of Zerglings at the start, at least five or six strong, is a good idea for defending your initial bases. Use this group to scout out your enemies location and to eliminate any scout units he or she may have. If you're lucky your enemy won't have built up a sizable force by then and you can even pull off an effective rush. This could spell out early victory for you but it is expected by veteran player. Zerg have the quickest units to spawn in game; they are less effective in small numbers but are great in huge swarms.
To achieve a huge swarm you're going to need a few Hatcheries, the more you have, the more you can create with each larvae spawn. This is very important because it can make or break the Zerg. In Starcraft 2 the Zerg have a number of ground and air units which are individually weak but are rather inexpensive to produce and make for excellent fighters in numbers.
The more Hatcheries you have the more effectively you can swarm the enemy, also, if your units are destro[censored] and your economy is still strong you can reproduce a large force relatively quickly.