Okay, Terran vs Terran. This means I should go for mech, since that's the defactor TvT strategy. I build up my base and start to pump out Siege Tanks and Thors. Before those go out though, I send out a scout to my opponent's base.
It's not there.
Okay, he's Terran, so he probably lifted off the Command Center in the beginning and is building up somewhere else.
Scout around the map...
I find him. And his base is REALLY close to mine. By now I've got some Siege Tanks and Thors, and he couldn't have teched (verb check on aisle 3) very high since he would be so delayed from having to move his base all the way over there. ATTACK!
I wipe up that base pretty bad, but then some air units start to attack my base so I have to retreat to deal with them.
And here's where I screwed up. I never went back to finish off that base. I went everywhere else in the map but there. But I never finished off his first base with the 3 Starports for air units.
Guess what I lost to. A massive air attack with Battlecruisers.