QUEEN TACTICS
Author: Daktakpaklak

The queen is a very important Zerg unit.  As soon as you've upgraded your Hatchery to a Lair, mutate a Queen's Nest and morph three or four Queens.  At the same time, research the Spawn Broodling ability and Meta-Sympatic Node upgrade.  Since Queen energy takes awhile to recharge, the abilities should be fully evolved by the time the Queens are energized.  Have Queens stationed in every region your units are operating; their Broodlings will destroy nearly any land unit in a single shot.  Broodling anything of value.  Particularily jucy targets are Templar, Siege Tanks, and Ultralisk.  Note that air units, Spider Mines, Reavers, and all Archons are invincible to Broodling.

Having a pair of Queens flying around the map is a great way to sabotage enemy troop movements.  Five or six Queens can easily take out a platoon of Dragoons with their Broodlings.  Sometimes you'll get lucky and happen upon a lone Templar or Siege Tank.  Nothing is more frustrating than being unable to safely move expensive land units around the map. To counter the threat of Broodling, simply keep your expensive vehciles in transports. Whenever an attack is eminent, simply unload the units into position. Queens are best destroyed from the air, since air units are immune to the Queen's abilities.

Parasite every Critter you see.  Since many players bon't bother to kill them, Critters provide excellent intelligence on enemy troop movements and expansions.

Capitalize on the long range of the Queen's abilities.  Parasite an enemy unit.  When you gain the ability to see what its seeing, Parasite another unit that is farther out.  This can allow you to see your foe's entire base without entering the range of their defenses.

Whenever possible, be sure to bring a Queen when attacking a Terran base.  Besides being able to Broodling expensive vehicles, the Queen has the inherent ability to Infest a Terran Command Center whenever the building has less than 750 HP.  The Infested Command Center can then be flown to a new location.  Infested Terrans are extremely useful splash defenders, performing particularily well against large groups of enemy units and enemy Ultralisk.  A warning: Infested Terrans are nearly as powerful as nukes, and it is easy to destroy friendly defensive units and structures with their blast.  Use them carefully!

When faced with parasiting multiple targets, consider the following criteria before making your choice:

Enemy transports make excellent spies.  Attaching a Parasite to a transport is advantageous for many reasons. Transports will return to base for more units, therefore showing you the location and contents of an enemy's base. They'll warn you of incoming invasionary forces. You'll be able to see to where he is expanding.
When a detector (Overlord, Science Vesel, or Observer) has been parsited, the units detection ability is retained. Effectively, you'll be able to see all cloaked enemy units that the parasited unit can!  If many of his detectors are parasited, it can be difficult for an enemy player to make effective attacks. Including a parasited dector with his attack force will not only result in you being able to see cloaked units that are part of his attack, but your units will also be able to target his parasited detector!
Parasiting cloaked units effective removes their cloaking ability to you. Ghosts will no longer be able to conduct a nuclear strike. Enemy Wraiths, Lurkers and Dark Templar will no longer be a problem.
Another way to effectively remove cloaking is to Ensnare enemy units. Cast Ensnare on the shimmer of the attackers.  Even though the enemy is cloaked, you can now target their units with your forces. This is an extremely effective way to counter problematic Dark Templar.

Refer to the section on Effective Nydus Canal Tactics to view more uses of the Queen's Parasite ability.