Carl's Guides

First get your military units grouped and hotkeyed to help stave off any early attacks by the zerg. Next, get your economy running. I recommend ten SCVs on minerals and three on gas. You need a good defensive force and bunker coverage early in this mission as you're all that's standing between the zerg and protoss. So get some marines and siege tanks w/ siege mode set up in defensive positions. A bunker with a siege tank next to it is a nice defensive tactic. The tank can soften up the approaching attackers and the marines in the bunker can finish them off. Build these at the northwestern, northeastern, eastern and southwestern entrances to your base. All the entrances should be covered by one siege tank in siege mode, ready to soften the attackers. Finally, don't forget about anti-air defenses. You need the stopping (and distracting power) of good missile turret coverage to prevent attacks from both the protoss scouts and zerg mutalisks. After that's done you can begin concentrating on upgrading your units and mounting an attack on the protoss.

Since this is your first time fighting the protoss you may be a bit suprised. They are vastly different from the other races (one of this game's main strengths is the diversity) and require some different tactics to be defeated. Unlike the other races their main detector/defensive structure is both anti-air and anti-ground. They all have shields and are generally tougher than other units in the game. Their zealot is definitely the strongest of the standard units and can really take some damage. Not to worry though for in this mission you can build your first battlecruisers. Not to say you should just build a couple of them and go charging into the enemy base but they can be a powerful asset and should be used to support your units from above. Especially since the annoying zealots can't touch them!

When you've amassed a force of 12 marines, 4 siege tanks, 6 goliaths and 2 battlecruisers leave your base with them (leave at least some marines behind to defend and if you're feeling extra careful leave them a battlecruiser to help) to the northeast. This base is simply the closest of the two; that's the only reason I picked it. Use the siege tanks from afar and keep units nearby to guard them. If things are starting to go wrong use the stimpack ability of your marines to make them go berserk and deal as much damage as possible. Sacrifice them to protect the other units. If your attack fails completely in the end (there are a lot of protoss here) don't fret. Just rebuild your forces and go back and finish them off. If you're running low on funds you can set up an "outpost" to the southwest of your base. There're plenty more minerals there and no enemy base protecting them.

The final base to the southeast should be easier than the first as you have the elevation advantage. Set up your siege tanks right at the edge and strive to cause as much damage as possible while the protoss try to send units up the ramps to attack you - block them off with your marines and goliaths. If you see a key protoss pylon, destroy it with the Yamato gun ability of your battlecruisers. Protoss buildings require this structure to deliver power to them. When this base is eliminated you'll be victorious unless the Protoss have attempted to start a new base in which case you can probably destroy it quickly once you find it.