Zerg Tech Tree
If you want to be a successful Zerg player you have got to get the zerg tech tree down cold. Learn which units are available at which structures.
Know the build orders that go with any particular strategy.
Are you planning a Speedling Rush? Know when to drop your pool. When and how to get the metabolic upgrade that turns your Zerglings into crazed steroid charged Speedlings.
Maybe your scouting efforts reveal that your enemy has no anti air defense. This tells you to start pumping out air to ground units. You have to know how and where to get your Mutas.
Once you choose your race you need to spend time learning the zerg tech tree. Understand the structures and upgrades, which units come out of which buildings.
The easiest way that I’ve found to begin learning the zerg tech tree is to choose a relatively simple strategy like the Speedling/Baneling rush and hone it to a razor sharp edge by practicing against the computer. The shokz guide has the strategies you need.
Increase the AI as it gets easy to win. Then hit the battlenet for some 1v1.
“Once you know the zerg tech tree inside and out you are well on your way to the next level up”.
Zerg Unit Guide
Here’s an excellent unit guide put together by GetJesse. This is from the beta version and there have been some changes but over all you get a great breakdown of the different units available. GetJesse also goes into great detail about each units unique abilities and available upgrades. He also points out differences between Starcraft 1 and Starcraft 2 units, abilities and upgrades.