Build a base...:
In a land rush, I try to find an area with thisck cliff cover and some okay ore access. For everything else. I try to build up in a defensive pattern, buildings with the strongest armor up front behind layers of gp's
Attaking...:
I prefer having the killing blow as an explosive attack. Supernova lynx's are my favorite (quick and a nice radius). My main tactic against the computer is a diversion of tigers to draw the units to one side while I have lynx come in and take out vital structures from the other.
Defending...:
Cliffs are a must! I use them to fend off rushers. If they can't get to my cc easily, they can't rush me.
your morale is dropping...
build more happy structures
the enemy colony prepares to invade...
send out all existing forces to weaken them, build up more forces to take the brunt of the remaining attack. Bulk up mining operations to allow for extra construction (vehicle factories, gps, walls...)
the lava and blight advance whitout mercy...
Use the lava as a sheild, the blight can't go through it.