Starcraft 2 Observer tactics are good to know for a wide variety of reasons. While playing StarCraft 2 in general, knowing the moves of your enemies can mean the difference between victory and defeat. When using the right mode of scouting, it's also easier to know how much assistance, and how many assets, are available that can help you to win. There is more than one type of observation that will help to keep a player on top, but the kind that is chosen by a player will depend on his or her individual preference.
Hovering the Observer over production buildings will show how many units are being created. It's well known that this is important information because units and buildings productions are important parts of the Starcraft world.
While deploying the Observer you can also find out the amount of resources and supplies that are remaining for your opponent's bases.
Be careful when deploying the Observer near anti air units as it has a distinct shimmering that an observant opponent can notice. If an Observer is noticed the enemy can then bring detection along with anti air units in the area in order to destroy it.
Observers are normally the first unit to be built from the Robotics Bay as they are required for scouting your opponent. They are also especially important against Terrans in the early game as they can detect cloaked Banshee units.
You should also bring an Observer with your own army as they have a variety of uses against the other races. Against Protoss opponents they can detect hidden Dark Templar for example, against Terrans they can detect Ghosts and Banshees and against Zerg they can detect burrowed units waiting to ambush your army. Observers can also detect Creep Tumors for your units to destroy.
Apart from the observer the Protoss have only the Photon Cannon for detection, as a result it's important to always have Observers out on the field. The Observer can be upgraded to have faster movement speed, however the resources and time spent is usually better invested elsewhere. One should also note that unlike other flying detectors such as the Overseer this unit is very fragile and will fall easily if it's detected.
Knowing how to use the Protoss Observer will serve all Protoss players well. To make the best of one's observation methods, it is also good to talk to other Protoss players for advice. Browsing the Internet can also help, as it will allow an individual to read diverse advice and tips.