I'm not an amazing player. I quit from all my placement matches even though I would have won 3 of them by just doing a worker rush (amazing how well that works sometimes), I still quit. Right now, I'm just doing random, defeating Bronze guys, to get the Reaper portrait.
However, I'm a decent Terran player.
TvP - More or less one of the easier match ups for me because of my practice in the Beta. 3Rax 2Tech/1Reacter and I get a force of Marauders and Marines, I get Stims/Shield/Concussion from the tech lab. After 3rd Rax, I get in a Ghost Academy and get the Moebius Reactor. Once I have around 20 troops, I attack. EMPing Toss units along with kiting any zealots does the trick pretty damn well. If I don't win the initial attack, then it becomes a scouting game. If I see a Dark Obelisk, I go to get Ravens out. If I see Void Rays or Colossi, I get Vikings. If I see Immortals, I get another Rax with a Reactor going to pump out more Marines. If the guy is going Charging Zealots, then I get some Banshees to compliment my Bio Ball. If the guy keeps going with Stalkers and Zealots, then I normally keep building Bio and add in a few Medivacs so I can fully stim.
TvT - I get a Rax with Tech and get Marines out to fight off any initial rush. Then I go straight to Tanks, and I scan to figure out if I should get Banshees or Vikings.
TvZ - This is the hardest match up for me because of the unpredictability of a Zerg player. The beginning is the same as a Toss match except for the lack of a Ghost. But after the initial Rauder/Rine push, it all depends on figuring out what the Zerg player is planning and getting the counter out. If he's going Air, then Missile Turrets need to be placed at the mineral line and Thors and Marines need to be pumped out. If he goes Roaches and Hydralisk, then you need a Rauder/Rine meatshield with Siege Tanks supporting. Hellions aren't that great against Hydras, so I don't recommend getting them out. Tier 3 units like Brood Lords and Ultralisk I don't really know what to do against because I never get that far in my Zerg matches.
With that said, it should be noted that a Zerg player might do some really unexpected stuff which is really why as a Terran you need to scout more with Zerg than Toss or Terran. Zerg players can switch up their production more or less immediately where as Toss and Terran can't. Once Toss and Terran place a production building, there's only 4-5 units that can come from there. One game, I was trying out a Marauder/Thor combo, which was working decently well against the guys Roaches, Hydralisks, and Mutalisks. I destroyed the guys main base, and was moving to an expansions when I found that the player had made 6 Hatcheries there and rebuilt his spawning pool. He then massed Zerglings and didn't stop building them. This was near the beginning of the Beta for me, so I by the time I realized that I needed to start spamming hellions, I had already lost about 4 75 supply armies to massed Zerglings. By the time I was getting hellions out, it was too late and I lost the match.