For a good portion of the game, you'll want to concentrate on simply
churning out Zealots. Optimally, have three or more Gateways constantly
pumping out Zealots, if you can afford it. These units are the least
expensive in the Protoss arsenal, but that doesn't mean you should
ignore them. Once you get your Zealots close enough to the enemy, they
will maul his units. Since Zealots cost only minerals (and no gas), you
won't have to worry about building an Assimilator quickly like the Zerg.
In the beginning, concentrate on gathering minerals to buy Zealots. Once you saturate your mineral fields with Probes, sending more to gather minerals probably won't improve the situation-now it's time to build your Assimilator. Don't bother building a Forge or Cybernetics Core until you have an Assimilator and are already rapidly gathering Vespene Gas. The Forge allows you to upgrade your units and allows you to build Photon Cannons. However, you can't upgrade your units unless you have the Vespene Gas, and in the beginning it's more worthwhile to build two Zealots than one Photon Cannon. The Cybernetics Core is a requirement for the more advanced buildings, but the more advanced buildings require a lot of Vespene Gas for construction.
Use your first two Zealots for scouting. When you have about eight Zealots, send them out to attack and have your scouting Zealots join the main attack group. Split your attack group into two smaller groups, so that your Zealots don't end up trying to chase a single retreating enemy unit while other ranged enemies are hitting you.
After the game has progressed a bit, you'll want to take advantage of the
Protoss aircraft to establish complete air dominance. Use Scouts to
attack enemy air units, but don't use them to attack ground units if they
can fire back. If you see Zerg Scourges or Queens, be sure to take them
out of the game quickly. Scouts are much more effective with the speed
upgrade, which allows them to fly in, fire off a volley of missiles, and
retreat. Against many types of enemy aircraft this tactic will allow the
Scouts to retreat unscathed, leaving behind a crashing enemy aircraft.
Recharge your Scouts' shields at a Shield Battery after such an attack.
Air force management is the key to the game. Your Scouts should huddle near your Carriers, and leave the pack only to attack enemies that are attacking your Carriers. Otherwise, let your Carriers do their work from as long range as possible, where they are less susceptible to enemy fire. Use Carriers to attack any enemy units or structures that can fire back as its first priority. Once there is no longer any resistance, then and only then should you try to attack enemy ground units.
Always bring an Observer or two with your aircraft when
playing against Terran opponents, whose cloaked Wraiths
could prove to be an annoyance.
If you are playing an island map, build a Robotics Facility early on to
allow for expansion. Each shuttle can fit four Zealots, which together pack
a considerable amount of power. Always bring along Zealots to protect
your Carriers. Whenever your opponent has ground units that can attack
your aircraft, send in the Zealots to snuff them out. If you can give your
Carriers free reign of the skies, you probably have the game sealed.
You can stack Carriers on top of one another, thus making them appear fewer in number to the enemy. Yet, this ability is extremely dangerous. One or two Psionic Storms or other special abilities can wipe out your entire fleet in one go. Spread your carriers out!
Against Protoss players, build Scouts before building Carriers, otherwise your Carrier will just get bulldozed by enemy Scouts. After building your first Carrier, you should probably consider expanding to a new mineral field. The Carrier, coupled with your Zealots, can usually adequately protect your new base. You usually only need one Probe to establish a new base, since a single Probe can begin the construction of multiple buildings simultaneously.
After you establish your second base and the resources begin to flow, immediately build a Citadel of Adun and research the Zealot speed upgrade. With the speed upgrade, the Zealot overcomes its disadvantage of having no range attack. Next build the Templar Archives. The Templar is a relatively inexpensive unit that proves to be a worthy investment-its Psionic Storm spell kills enemy units with aplomb. Psionic Storm works best when your opponent fighting other members of your forces. If you have large numbers of Templars but no regular troops or aircraft, your enemy will be able to quickly kill off all your Templars because they have such low hit points. Instead, Templars should lurk around in the rear of your army away from the heavy fighting, ready for use once the enemy approaches. Use the Templar's Psionic Storm ability in the path of incoming enemy attackers, and when they arrive to attack they will all be greatly damaged and easy pickings. Use it when attacking an enemy base, and it will force him to come out to meet you away from the safety of his base defenses.
The strengths of the Protoss really shine late in the game, after you've
deployed its full arsenal. Scouts, with the assistance of Carriers,
dominate the skies. Swarms of Zealots, the Templars' Psionic Storm, and
Carriers providing long-range support control the ground. Special abilities
like Hallucination and the Arbiter's Cloaking allow Protoss players to
maximize the effectiveness of their forces.
The Templar's Hallucination ability will begin to play a significant role late in the game. Not only do Hallucinated units cause your opponent to vastly overestimate the strength of your military, but they have immense offensive potential as well. Put the weaponless Hallucinations in the front of your attack force and they will draw most of the fire, allowing your real units to attack freely.
Arbiters also begin to play a role late in the game, and can make the difference between victory and defeat. The Arbiter cloaks all nearby units, and if your opponent isn't expecting it you could easily wipe out his entire force in an ambush by cloaking your air fleet. Arbiters will also allow you to win battles in which you find yourself greatly outnumbered and outmatched. Use the Stasis ability to paralyze clumps of enemy units, so that you deal with the enemy in small groups instead of the entire enemy military in full force.
The Photon Cannon is a respectable defensive structure that has both an
anti-aircraft and ground-attack weapon. However, the Cannon is only
effective in large numbers and with unit support. Left alone, the numerous
long range weapons like Zerg Guardians, Protoss Reavers, and Terran
Siege Tanks will rip the Protoss defensive structures to pieces.
The Photon Cannon's best feature is its cloak-detecting capability. If you want a powerful defense, the Shield Battery is the better replacement. It will recharge your units' shields on a moment's notice. Surround a shield battery with Dragoons, and whenever the Dragoons get damaged simply recharge their shields-you can beat back large-scale air raids with such a strategy. The same strategy works just as well for any other ranged unit, such as Carriers. Unless you are massively outnumbered, Carriers positioned near a Shield Battery (and recharged constantly whenever hurt) should hold up against almost any attack.
