Massive armies can win battles.  
A superior economy can give you the
advantage to win battles.  However,
the
most often overlooked resource of modern RTS gaming is intelligence. style="">  In StarCraft II, this is
no different.  The
knowledge of what it is, and where it is
regarding your opponent’s army is invaluable. 
Proper scouting is key to victory, and there are a few
ways to go about
it.

href="http://www.tentonhammer.com/node/86222"> src="http://www.tentonhammer.com/image/view/86222"
style="border: 2px solid ; width: 150px; height: 200px;">

style="font-style: italic;">This man may not look like much,
but not only will he harvest everything you need over the course of the
game, but also give you the majority of scouting intel you could ever
ask for.

style="font-style: italic;">But he might die trying, too.

The game is won with intel on your opponent!

It falls unto the lowly worker to venture out into the dangerous
wastelands to find where your opponent is.   When you
specifically choose scout is up to you, but if you are against a Terran
it needs to be around your 9tth or 10th worker to ensure that you can
get in before they wall off.   Of course, the
opportunity cost of sending a scout out that early is huge when your
mineral patches are nowhere near saturated.   The
cost of defeat when you can’t see that your opponent is fast teching to
Banshees is even greater though.



Step 1 – The Hotkey



Most people balk at this, but take your scout and make it a Team via
the Ctrl+# of your choice shortcut.   Should you see
something, pressing this twice will instantly center the screen on your
scout and give you a status update.  You need to be able to
issue accurate commands very quickly, but at the same time, not forget
that you have a budding base back at home that needs constant
production of workers and an eventual teching up to your units of
choice.  What are those units?  That’s what this
worker is trying to find out.



Step 2 – The Dance



Once the scout is in, your goal is to keep it alive as long as
possible.  Move to every corner of their base and get intel on
everything that is happening.  Is there a pylon in the
corner?   Make note of it and scout it in a minute if
your scout dies to see if a hidden tech switch is happening. 
Are there two barracks with tech labs down?  If so, there are
a lot of Marauders in your future.



Advanced Scout Tactics



First, you can queue actions.  Hold down the shift button and
right click a few times in a circle of way points, and your worker will
evade attackers and chasing workers for a while so you can manage your
base.



Second, don’t be afraid to use an offensive building as a scare
tactic.  Many people flip the moment they find a pylon in
their base.  A hidden bunker can lead to a scary siege
later.  And drones can even heal and free up an additional
supply for a split second by building an Extractor and then cancelling
it.



Countering Enemy Scouts



Knowing your opponent has a scout in your base is
frustrating.  You need to get it out ASAP while not
sacrificing too much to get it out.  If you suspect a possible
hidden pylon or other building, send one of your workers on an attack
command at it.  If they fight back, send a second and have the
first one return to mining.



Workers can run faster than any basic unit aside from the
Zergling.  Proper control and waypoint usage can keep your
worker alive until Stalkers hit the floor versus Protoss, so rush to
ranged units if you have a scout preventing you from making your next
tech move.



Scouting Further



When the worker can no longer get to where it needs to go, what do you
scout with next?  Another worker.  You might balk at
this, but the majority of the time in the mid and late game you’re just
trying to keep tabs on their expansions and their army.  This
does both for you.



Should you need to reveal more, everyone has a trick up their sleeve to
make it simple to be aware of your opponent’s plans!



Terrans – Floating Buildings go a long way.  Usually you’ll
have an idle barracks sitting around.  Fly it around the
map!   Use the waypoint shift-queue system to set up
a series of orders to have the barracks fly between bases, fly in the
back of your opponent’s base, or hover over vulnerable siege positions,
or dropship routes



Zerg – Overlords, overlords, overlords.  Overlords should be
everywhere, and if your opponent realizes you have an overlord at every
resource expansion on the map, you might need to scramble to defend
them.  Map control is one of the most vital parts of the Zerg
game, and Overlords give you the intelligence needed to gauge your
opponent’s progress and adjust your plans accordingly.



Even with the addition of new spells to the Overseer, your predominant
usage of mana is going to be to spawn Changelings for free scouting and
possible infiltration.  Hide them anywhere and everywhere,
especially alongside the units they blend in with.



Creep Tumors also provide a solid sight radius, and can basically leave
half of the map fully visible under your control if left
alone.  Most players won’t bother to hunt and destroy these
tumors, so take advantage of this and reveal everything you can—and get
the speed bonus from the creep as well!



Protoss – Observers of course dominate the stealth recon game, but a
random Dark Templar can get you intelligence and cause your opponent
much grief.  Throwing one every now and then at your
opponent’s undefended expansions can reap far more rewards than an
observer noticing it.



Hallucination provides one of the best scouts in the game—whatever you
want it to be!  It’s free and it can take a decent bit of
punishment before it goes down.  Hallucinated Phoenixes can
see almost everything every time before they die to gunfire.



In StarCraft II, victory is decided by knowledge.  With so
many counter units and so many devastating abilities that require a
specific counter, you have to be armed with the knowledge of what your
opponent is getting.  A generic army may win sometimes, but if
your opponent focuses on something unorthodox, you may get
steamrolled!  Scout early, scout often, and never let your
opponent have the advantage of surprise!