Heart of the Swarm Campaign- Korhal: Planetfall

The third to last mission of the game, this is where you finally gain the evolution mission for ultralisks.  At this point, though, they are unlikely to be vital to your forces- you've been going without them for so long that you're probably accustomed to having aberrations instead.

The mission opens with Kerrigan and some core forces arriving and establishing a main ground base.  Your immediate task is to build up an attack/defense group that can keep the bile launchers alive as they arrive on Korhal's surface.  To this end, invest in resource gathering and reinvest those resources in more gathering for the moment.

Almost immediately, Izsha will alert you to the pending arrival of a bile launcher to the West of your starting location- you need to have a group of Zerg ready soon to protect its location.  Just before the launcher lands, a small cluster of marines will attempt an assault on your base from that direction.  Your initial 'free' units should be plenty to take care of those, even without Kerrigan.  When the launcher lands, it comes with a pair of spine crawlers which you should root as soon as a good location is available- the Southern edge of the crater immediately to the North of the launcher location is a good spot.  A second Terran assault force should move in soon- again, the units you have by default will be plenty for dealing with this attack.

By the time Izsha marks the pending location of the second bile launcher, outside your base to the East, you should have started building up your forces with additional units.  Make sure you send the bulk of your potential attackers out to protect the location; it's pretty much a given that the Dominion is aware of where the drop pods that are making it through the planetary defenses will land, and is thus making their attacks specifically via those routes.

Don't forget to reinforce the West end of your base even as you build up units for protecting bile launchers- while they may not have started yet, the Dominion troops are going to be trying to take out the launchers that you have already defended and seen entrenched.  As the second bile launcher comes down, Zagara will point out the location of several large heavy gates  which can be used to send troops into Augustgrad.  These bonus objectives are located on the far East side of the map, near the center of the North side, and in the Northwest corner.  The East gate is close to your forces' current location, so breaching it should be at most a minor distraction.  Similar is the Terran base in the Southeast corner- though heavily defended, it and its defensive forces are small and can be quickly destroyed with a solid attacking group.