TotalBiscuit has a series called I Suck at Starcraft where he comments on his own noob games, focusing on what mistakes were made and how to improve.
The series starts out very basic, explaining economy, supply, teching, and the uses of some individual units. It should be understandable even for someone brand-new to SC2. The downside to this is that it may be too basic for many players. However, over the course of about 15 videos, he moves into (somewhat) more advanced concepts.
Barring scouting some kind of all-in rush coming from the terrans, you should probably be expanding before the 26 food mark. Personally I would recommend 14 pool, 16 hatch, and getting two gas geysers up at ~21 food. If you want to play it safe though you can go 14 gas, 14 pool and get the hatch around 24. If you want to be a little risky for more economic gain, go 14 hatch 14 pool. The larger the map/distance between you and your enemy the safer the fast expand is. I would generally recommend getting speedlings with your first 100 gas, and a baneling nest with your next 50. Banelings are never a bad thing to have vs terran.
As for mid-game, muta-ling is generally superior to hydra-roach in team games, as the bigger maps makes the mobility and map control provided by the mutas and speedlings more powerful.
If you are falling behind, you likely are not building enough drones early. Drone hard early game, keep lings at the towers and one outside their ramp to spot when you need to start pumping units like crazy. With two queen boosted hatches you can get a lot of lings out by the time they walk across the map.
Personal Credentials: 1200+ diamond 2v2 team with both of us playing random.
Best Answer
Terran is extremely versatile. In GSL, where you have to face many opponents with varying playstyles who have had a chance to study your previous games, you can easily be sniped. The best Terrans, like MVP, are capable of playing dozens of different "standard" styles effectively. On the other hand, the best Zergs and Protosses are still funneled into three or four basic "standard" strategies that don't allow much room for strategic innovation or trickery.
On ladder, you'll rarely see anyone enough to get a good grasp of their playstyle and how to go about countering it, but teams in GSL specifically prepare for days to match up against one opponent. Additionally, there has been talk that the 1-1-1 build is the root of the problem because it allows so much versatility to either expand or hit incredibly hard-to-stop pushes.
Finally, Boxer and Nada were two of the first to switch from professional BW to SC2. In Korea, their influence should not be underestimated- they are probably the two biggest names in competitive StarCraft ever and that's liable to cause a good number of up and coming players to favor Terran. This is most notable on the SlayerS team, which is made up primarily of a number of incredibly good Terran players, all new faces: MMA, Ganzi, Ryung, Taeja.