StarCraft: Brood War/Protoss Mission 1: Escape from Aiur

From Start to the Nydus Cluster
To ease you into the campaign of Brood War, Blizzard decided to start the first mission with a modified installation scenario: similar to missions like The Jacobs Installation and The Amerigo from the original StarCraft, you are given a limited number of units to control with no base and scarce reinforcements. You'll be following a set path through the valleys until you reach the end of the map.

You start with Zeratul, six Zealots, and three Dragoons. Split them into three hotkeyed groups, and start down south, leading with Zeratul. You can kill most resistance in this first leg of the journey using Zeratul alone; only when a large number of units start surrounding the hero are the other units necessary. You'll pass a couple Nydus Canals along the way; these will pump in a steady stream of enemy Zerg, so have Zeratul use his massive damage to cut up the Canals first while the Zealots and Dragoons kill the Zerg units that attack him.

About two-thirds of the way down, you'll meet a couple Zealots who tell you that there's no time to lose. Follow the Zealots to discover a large skirmish occuring between about a dozen Zealots and Zerglings/Hydralisks. The Zealots aren't in a bad position (they're in a line, so Zerglings can't surround them to attack effectively), so leave them to fight while Zeratul sneaks between the lines to kill the Nydus Canals in this cluster. Your own starting units can help the Zealots fight, but be careful not to lose any Dragoons.

When it's over, you should have more Zealots than you started with—if you're lucky, you might have more than a full group left.

From the Cluster to the Protoss Stronghold
Continue to follow the path. You'll get to a juncture soon, with one path leading north and one to the east. Go east, where you'll find a couple more Zealots fighting Zerglings coming out of a Nydus Canal. Give them a hand, and you just got yourself more reinforcements.

The juncture eventually leads to the same place, and there's nothing to see by going north anyway. You'll come to a harmless-looking Sunken Colony; since Zeratul is cloaked, you might consider using him to take it out quickly. However, there's a Spore Colony just out of your sight past that Sunken, and while Zeratul can still handle it if he has more than 100 or so shield points left, it's not really worth it. Just rush the Zealots in to take out the Sunken Colony plus its twin right beyond the Spore Colony. There's also an Ultralisk Cavern here, which means there are—you guessed it—Ultralisks around. More specifically, there are two of the monsters hiding beyond the corner of the valley. Have Zeratul and the Zealots surround the Ultralisks, and they will go down in short order.

There's another split in the valley a bit after this point. Taking the east route circles around and takes you to the same place as you would be if you went north, but there's an additional four Zealots fighting a lone Ultralisk along this path. Take Zeratul around that path to discover the Zealots and recruit them.

Eliminate the small Hydralisk defense along the northern route, and you'll find yourself in a small but operational (as in, the Pylons are actually working) Protoss stronghold. Use the two Shield Batteries here to recharge everyone, making sure that Zeratul is back to his 400. Group all the new guys into your existing hotkeys, making a second group of Zealots if necessary and putting the Archon with the Dragoons.

From the Stronghold to the Warp Gate
Heading east from here reveals another Nydus Canal... with a large number of Hydralisks Burrowed around it. while having the Dragoons close by and Holding Position for defense, take the two High Templar and Psionic Storm the area once with each Templar to thin out their numbers. Then, move Zeratul and the Zealots in to rip up the stragglers.

Move south to come to another Sunken-Spore combo. There are a lot of Zerglings and Hydralisks hiding here as well, so take the High Templar and Psi Storm as many times as their energy will let you in the area around the Sunken (of course, make sure that you're not actually getting within range of the Colony). Once they're spent, combine them to get another Archon and group it with the Dragoons while Zeratul and the Zealots move in for cleanup.

From here on down, it's just a series of small Zergling or Ultralisk patrols that you can simply attack-move into. If you wish, Zeratul alone can just go down to the Warp Gate (the location of which was revealed to you midway through the mission) by himself to end the mission, or you can take everybody else along as well.