I am not sure how helpful this is going to be to Advanced players, but I'm sure that newbies to intermediate players can gain from this advice: You see, the Protoss race is a race of pure power, unlike the terran race which involves complex tactics and sneaky actions. This makes it easy for all levels of StarCraft players to use them. With Protoss, I would begin having all four starting Probes gathering minerals and with the first 50 minerals, obviously build a probe. As soon as this Probe comes out of the Nexus, send it to work. Repeat this process until you are prompted to "construct additional Pylons". At this point you may have to wait a few seconds in order gain 100 minerals to get a pylon. Once you have enough minerals, build two starting pylons, (not next to each other) somewhat near your Nexus. Once they develop, build two initial Gateways between them, and set rally points for the entrance of your base. After you have about five, maybe six Zealots, build a forge and a new set of Pylons around it. This will enable you to build photon cannons (a very key defense mechanism). Build two Pylons, one on each side of the entrance to your base. On each side build about 5 photons around each Pylon. (Make sure you leave enough room for Dragoos to get through, they can be a bitch to keep under control). Don’t forget to continue to check your gateways through all of this, so you have enough offence if you are rushed. Now after you have a decent amount of Zealots, I'm sure you’re getting bored of them. Build a Cybernetics core, which will allow you to build Dragoons. While this is building, build two Assimilators, because Dragoons require Vespean. Now, you have some Dragoons (for air and ground), some Zealots (for ground) and some Photon Cannons (for defense). This should last you most of the game, but you will need more gateways, and some more photon cannons. So do this, and get about six or seven gateways, and cannons all around the perimeter of you base. Don’t even bother with air unless you are like an hour into the game and nothing is working.
Now If you really itching, for more units, go with Dark Templars. For this, you will need to build a Cidadel of Adun, and then a Templar Archives. Build up an entire army of these, and Get just as many Dragoons, (for air) and you are ready to send your final wave of attack, leading to glorious victory.

CreepColony's Opinion: Not many people would agree on the "don't bother getting air" thing. It really depends on what kinda game it is and what your opponent is making.