Shit you didn't think about when you played Terran
Don't build a reactor on a rax unless you're going to switch it to another building. BUT PAT MY RAX SHOULD HAVE ADDONS! The fact of the matter is that a reactor is 50/50, with a build time of 50 seconds. You lose 2 marines effectively to make it, plus 50 gas. Another rax is 150/0, with 60 second build time. Terrans have MULEs so mineral income is always going to be higher than gas income. Don't waste gas and marine production making rax reactors unless you really need the space!
In fact, gas income is fixed at 114 gas per minute per geyser. You should have a plan for your gas, including when to take a second base. Your expo timing should be about when you need the gas income. Vikings and tanks aren't exactly easy on your gas. If you get some extra gas due to shit macro, build upgrades rather than queueing or building an extra factory or starport.
DO NOT BUILD A REACTOR ON YOUR STARPORT IF YOU NEED SOMETHING FOR TIMING. If you're building Vikings for a push, it's best to build 2 vikings for your push, then get the reactor. Alternatively though, if you want a reactor right away, take one from a rax and build another rax to keep up your marine production. In fact, always do this. Starports and factories cost 100 gas, so a reactor is economical but don't slow down your main unit production to get a reactor. 50 second build times suck.
Always get 2 tech labs for rax. Stim, concussive shells, and combat shield are so retardedly OP and you want them now. Not 2 minutes from now.
Speaking of stim/concussive/combat shield: Stim is first if you're attacking. Concussive shells are first if you're intending to turtle. Combat shield should probably always be second. If you have 2 techlabs, research stim/shield or shells/shield. If you're hard up for gas (getting +1/+1 and marauders at the same time or something) then do the upgrades in the proper order.
Terran should get +1 attack before +1 armor.
Infernal pre-igniter is awesome if you're going for harass. It's not that great with a lot of hellions vs. mass lings though; a lot of hellions won't kill a ton more lings with infernal just due to how positioning works.
Speaking of hellions, they rape speedlings off creep with micro. I highly consider if you're going for 111 vs. zerg, getting hellions when you do your infantry push. Make sure to protect them though; they tend to run ahead and die like bitches. I'd put them in a second control group similar to how zerg uses speedlings.
There's a very small window for reaper harass vs. zerg. If you build your rax at roughly the same time as pool, you only have 20-30 seconds from when that first reaper comes out to when the zerg first queen comes out. Obviously zerg build pool a little later in general, but even with a 13 gas 14 pool, you have maybe 30-50 seconds tops to get your first reaper across the map before the queen pops and another 30 seconds after that before speedlings. This means if you reaper harass vs. zerg, you need to use 1 reaper to kill 3-4 drones for the reaper to really be worth it. A second reaper is almost useless vs. speedlings and queens outrange reapers.
Reapers vs. protoss are a little better. You have almost 90 seconds before that first stalker comes out. Zealots are no threat to a reaper, but a high ground base can still be shot down by stalkers. Killing pylons is the better deal here imo. 3 reapers can drop a pylon in 6 seconds.
Reapers vs. terran comes out a lot to skill. I don't know that I would try it vs. a skilled terran. If a marine fights a reaper, the marine will destroy the reaper. Fuck terran. Since Terran doesn't have a ground tower, reapers are pretty good at harassing midgame, rather than late game. 4 reapers will destroy depots in seconds.
Vikings are great at killing zerg spotters, but if the zerg army is forward, a spotter-killing viking will be in deep shit.
Going 1/1/1 if you're a noob terran and dropping will probably result in losing your drop and/or your base in a huge counter. Don't drop if you can't defend, unless you're hella pro.
Don't ever make battlecruisers.
Cloaked banshees are sneaky, but not a win tactic. Use them to divert the enemy's army away from important positions so you can attack.
In fact, gas income is fixed at 114 gas per minute per geyser. You should have a plan for your gas, including when to take a second base. Your expo timing should be about when you need the gas income. Vikings and tanks aren't exactly easy on your gas. If you get some extra gas due to shit macro, build upgrades rather than queueing or building an extra factory or starport.
DO NOT BUILD A REACTOR ON YOUR STARPORT IF YOU NEED SOMETHING FOR TIMING. If you're building Vikings for a push, it's best to build 2 vikings for your push, then get the reactor. Alternatively though, if you want a reactor right away, take one from a rax and build another rax to keep up your marine production. In fact, always do this. Starports and factories cost 100 gas, so a reactor is economical but don't slow down your main unit production to get a reactor. 50 second build times suck.
Always get 2 tech labs for rax. Stim, concussive shells, and combat shield are so retardedly OP and you want them now. Not 2 minutes from now.
Speaking of stim/concussive/combat shield: Stim is first if you're attacking. Concussive shells are first if you're intending to turtle. Combat shield should probably always be second. If you have 2 techlabs, research stim/shield or shells/shield. If you're hard up for gas (getting +1/+1 and marauders at the same time or something) then do the upgrades in the proper order.
Terran should get +1 attack before +1 armor.
Infernal pre-igniter is awesome if you're going for harass. It's not that great with a lot of hellions vs. mass lings though; a lot of hellions won't kill a ton more lings with infernal just due to how positioning works.
Speaking of hellions, they rape speedlings off creep with micro. I highly consider if you're going for 111 vs. zerg, getting hellions when you do your infantry push. Make sure to protect them though; they tend to run ahead and die like bitches. I'd put them in a second control group similar to how zerg uses speedlings.
There's a very small window for reaper harass vs. zerg. If you build your rax at roughly the same time as pool, you only have 20-30 seconds from when that first reaper comes out to when the zerg first queen comes out. Obviously zerg build pool a little later in general, but even with a 13 gas 14 pool, you have maybe 30-50 seconds tops to get your first reaper across the map before the queen pops and another 30 seconds after that before speedlings. This means if you reaper harass vs. zerg, you need to use 1 reaper to kill 3-4 drones for the reaper to really be worth it. A second reaper is almost useless vs. speedlings and queens outrange reapers.
Reapers vs. protoss are a little better. You have almost 90 seconds before that first stalker comes out. Zealots are no threat to a reaper, but a high ground base can still be shot down by stalkers. Killing pylons is the better deal here imo. 3 reapers can drop a pylon in 6 seconds.
Reapers vs. terran comes out a lot to skill. I don't know that I would try it vs. a skilled terran. If a marine fights a reaper, the marine will destroy the reaper. Fuck terran. Since Terran doesn't have a ground tower, reapers are pretty good at harassing midgame, rather than late game. 4 reapers will destroy depots in seconds.
Vikings are great at killing zerg spotters, but if the zerg army is forward, a spotter-killing viking will be in deep shit.
Going 1/1/1 if you're a noob terran and dropping will probably result in losing your drop and/or your base in a huge counter. Don't drop if you can't defend, unless you're hella pro.
Don't ever make battlecruisers.
Cloaked banshees are sneaky, but not a win tactic. Use them to divert the enemy's army away from important positions so you can attack.