Glon's Zerg Guides
Quantic Glon's TL-Strategy approved guide for all intermediate-level Zerg players deals with the various strategies and builds of the other races. While some parts of the game have changed with HotS, the foundation remains the same.
Glon's Zerg vs Protoss
In general, when scouting, you should remember two timings: 6:30 and ~10:00. At 6:30, the Zerg player needs to scout the Protoss with their 2 Overlords; the first Overlord moving into the main to attempt to see any tech buildings the Protoss player has warped in and the second Overlord moving into the Protoss natural to see how many gasses the Protoss player has taken.
Glon's Zerg vs Terran
Almost all builds in Zerg versus Terran start off with a 15 Hatchery. To deal with 2 Barracks play, I would heavily suggest scouting at 15 supply with a Drone. Send both the scouting and Hatchery-building Drones from your main mineral line at the same time, one building the Hatchery at your natural and the other moving across the map to scout your opponent. Alternatively, some players opt to go for an earlier scout, sent as early as 12 supply, if they feel insecure holding off 2 Barracks play. Each player should make their own choices on each map, depending on how confident they are on holding off this early cheese.
Glon's Zerg vs Zerg
Before we even start discussing build orders: your first three Overlords must go across the map. Generally, your first Overlord should head towards your opponent's natural, the second one to your opponent's third (or some place near it that gives you as much vision as possible), and the third one to the middle of the map where there is a good chance they can spot incoming early aggression. Future Overlords can be placed at your own discretion, though it may be a good choice to leave them near your base to keep them from being picked off.
There are three basic openers that can be done in the ZvZ matchup: fast Pool (on 6, 7, 8, 10, 11), standard Pool into expand, and Hatchery first.
3 Hatch Before Gas (vs. Protoss)
This build is the most common response to a Fast Expand from your opponent (generally either Forge Fast Expand or YufFE), and is currently the most widely used build versus Protoss. It delays taking your gas and unit production until the very last moment, taking advantage of the delayed Warpgate technology of your opponent. Should you scout a one-base play from your opponent, it is recommended not to plant your third Hatchery and diverge from this build, taking an earlier gas instead.
This build is designed to give you three saturated bases very quickly, while being safe against any timing attack from the Protoss player, in order to give you an economic edge over your opponent. If you are able to survive the mid-game pressure from your opponent, it is not too uncommon to be maxed on Roaches and Zerglings at the twelve minute mark while transitioning to Hive tech.