If you’re using the Protoss, the Dark Templar Rush can be a very effective and useful Protoss strategy. First, build a pylon with your second probe to be produced at the nexus. Use that same probe to scout the enemy and harass workers with Zealots. The goal of this Protoss Strategy is to go for the resource gatherers and cut off your opponents resources. This is a must in order to properly execute the Dark Templar Rush.
Chrono boost immediately on the nexus and micro your harass probe. Your goal here is to build as many structures as your resources allow. You also want to keep harassing your opponent which requires a good bit of micromanagement. If possible, build a pylon at your opponents natural expansion to prevent any units from escaping. Also prepare yourself for a reaper/zealot rush which will inevitably happen. Build a proxy pylon near your opponents base, but keep it HIDDEN and do not use (yet).
Once your opponent realizes what you’re doing, he’ll come after your base with everything. There’s a couple things your can do. Firstly, you can create a choke point at your base’s entrance. Place a zealot at the entrance and hold positioning to stop any front door rushes. You may also want to put a couple of stalkers behind the zealots up front. This Protoss strategy stops your opponent from attacking you in mass. Because of this bottleneck, they must send in attackers one at a time giving you the edge. A second strategy you can use, is you can build a Dark Templar at your base. This way if your opponent does try to attack he’ll have a pleasant surprise waiting for him. A third thing you can do is heavily fortify your base with forge canons which will help you block the entrance to your base. Any of these methods can work. Which one you decide to use is really up to you and what you feel comfortable with.
Get 2-3 more warp gates so you can mass later. If there are destructible terrain entrances to your base build a pylon. Don’t attack his army with the DTs, go for the structures. If your opponent has overseers or scan sweep don’t try to force your way into his base. If you find out he has one of these two, stop building DTs and move onto something else. Try getting a warp prism to drop the DTs behind your opponents base. The Dark Templar Rush can be a very effective Protoss strategy if properly executed, but be prepared. If your opponent is preparing for a Dark Templar Rush this Protoss strategy will be extremely hard to pull off and you should probably abandon it.