This can be a difficult match-up if both players are of equal skill. Since Protoss can be slow starting off, the phase of the game where the action begins to heat up is during the middle-game when there are better units. Usually, your Protoss enemy will play using one of the following types of build:
· Double gateway, straight zealots for defense
· Tech rush (could be rush to dark templar, carriers, dragoons,etc..)
· Cannon defense then development
· Early Expansion
· Containment
Remember, these are basic builds. There will always be surprises, but if you learn how to play against the fundamental builds, then you will be able to use logic to play against those random ones.

Double Gateways
This is the most common build for Protoss players. It has the advantage of having a strong and mobile early defense. Usually the player boosts along at a nice tech rate and then branches off from a cybernetics core to whatever tech he wants (reavers, air, dragoons ,etc..). This is the basic build, but "basic" does not mean it sucks. In fact, we recommend this as it is low in risk and relatively high in gain. Here is an example of this type of build. You do not have to follow this step-by-step. It is merely a guide.
· 8th probe builds pylon
· 10th probe makes gateway
· 12th probe makes second gateway
· 13th probe makes pylon
· begin pumping out zealots and making probes for minerals and gas. Never stop making zealots until you have at least 12 zealots. Then you should at least make one instead of two every time you can. Also, if you feel you can attack and do well then do it.
· Now you begin to get tech with a forge and cy-core. Upgrade weapons a.s.a.p.
· Now you have more minerals so you build like 2 cannons, possibly 2 more forges, upgrade goon range, build citadel, build gateways, and then slip into some branch of tech, which should be chosen considering what your enemy is doing.

This is a vague description of how to build this way. Please do not follow this to the word. Just take everything relative to everything else (e.g. "I build a forge after I build a gateway").
The best strategy you can use against this type of build is really the exact same thing. You have to beat your enemy at his own game. This really comes down to who is better. One slip-up by your enemy and you may have the game. When playing someone with this order it really comes down to the individual battles, which means you should consider unit weaknesses (which will all be described later) in order to choose an appropriate counter. The tricker you are the better you will do.

Tech Rush
The risk is high in this case but, the rewards are priceless. You can tell if someone is going fast tech by if they have gas earlier than normal (e.g. he has gas but no defense up yet) and by if they have higher tech buildings such as a cy-core and anything above that (If they have two cy-cores they are definitely going air, most likely carriers). They could be rushing DTs, air, or whatever. The weakness of this is they are vulnerable in the beginning. So the best build to use against this is the double gateway build, and use the zealots you make to keep the pressure on him; hell, you might even kill them. But be warned: If your attacks seem to be failing, do not neglect your base. Never neglect your base. He could be putting down all your zealots, and when he gets DTs, he is going to send them to your base where he will find nothing but two gateways and some pylons. So remember to keep your base up to tech. Here is an example of a DT rush order:
· 7th probe builds pylon
· Keep making probes until you have 150 minerals, then build gateway
· make another pylon and an assimilator
· build a cy-core a.s.a.p.
· put 3 probes on gas. You should still be making continuos probes
· build another gateway and a citadel. Get a second gas going when you can
· Build a templar archives, and when that warps in, make your DTs.
There are many variations of this. The preceeding example is very risky because there is no defense whatsoever before you get your DTs. You might modify it so you build a forge and two cannons along with two zealots.The last piece of advice for playing against a build like this is to use the type unit that is the counter to the unit he is using. If he is going fast goons then get upgraded zealots supported by templars and dark templars, etc...
cannon defense w/development

This is what newbies tend to go towards. We do not build this way as it sucks so we have no definite build order, but we can tell you the characteristics:
· Early forge (usually the second building he/she builds) followed by cannons completely filling their choke (entrance).
· Little or no map activity (e.g. expanding) of the enemy.
· Cannons all around the perimeter of his/her base.
· If you can get in their base with an observer and see a huge line of gateways/stargates/robo. facils./etc..
· Lots of buildings but no big units.
Basically, the idea is "sit in my 'well defended' base building up, and then I will send all my guys out ." These types of builds are favorite among "no rush-ers," who suck. They usually want 10 to 20 minutes of no "rush," which is stupid because attacking 10 to 20 minutes into the game contradicts the term "rush." A rush is like 5 minutes into the game.
What you should do against this build is take advantage of the ability to control the map. Expand wherever you want. Take the middle, and entrap your enemy. Just make sure that each expansion is so well defended that it could be considered a base in and of itself because when your enemy comes attackin' (50 minutes into the game) it will be one big giant mass of brute force. So unify your expansions, do not let a newbie pick off each one of your expansions, one-by-one. Also, during the middle of the game, screw with your enemy. He's a turtle. Drop him, mess up his front line cannons, forcing him to rebuild, waste his time,etc.. Don't be like him and just sit there. Take the initiative.
early expansion
This is risky but can be quite powerful. The idea is to make a second nexus at an expansion (usually the closest one) as soon as possible and then to set up a defense (usually cannons), and go from there. This can work really well, but it is easy to fall into "turtle" mode and rely on cannons. There is no specific build for this. It is just
· Gather minerals and make probes and pylons until you have 400 minerals, and then, make a nexus.
· Set up some kind of defense while making probes for the expansions.
· Continue as if you were playing the "double gateway method" except with more money.
To counter someone using this, it is best to attack early and to be using the "double gateway build" so that when you find them trying to expand with no units except probes, you will have zealots ready to go. If they do get past the vulnerable stage then A: you must expand a.s.a.p. and B: play them as you would any other person, paying attention to his/her strategy. This is tough, because they might be doing a combination of early expansion and tech rush so watch out!
containment
This is when your enemy tries to keep you in your base or out of a certain area either by cannoning your base entrance or setting up an expansion in the middle or right outside your base. If you see this early on, then they probably do not have much at their home base. So your best bet is to get DTs and templars and use some shuttles to drop into their main. And even if that drop fails, you should have been making more guys and siege units (reavers) in order to hastle is blockade. Really, the best method to counter this is to catch it as early as possible so that you may have time to react.
Please, check out the unit counters section so that you may attack your enemy's strategy directly with the right unit.