[ Terran ] 1/1/1 'Jack of All Trades' build

This is the most common strategy for the Terran race and can be considered the backbone for almost all Terran strategies. It was proven to be the most successful strategy against Protoss and eventually, Zerg as well. The 1/1/1 means that you will need to build 1 Barracks, 1 Factory and 1 Starport for starters. After that, you can proceed to build additional Barracks or Factory (or any buildings that you like).

The reason why this build is called 'Jack of All Trades' is due to the variety of different units that can be trained to counter most of the opponent's build (any race). The only down side of this strategy is that since you are concentrating on building technologies, you will have less army to counter any early push.

Build order:
1. Firstly, send the SCVs to mine the minerals like usual. Proceed by building a Supply Depot when you reach 10 cap (usually, the Supply Depot will be built at the entrance to your base to block any incoming units and this tactic can also be applied for Barracks, Factory and Starport).

2. As stated before, this build is vulnerable to early-game rushes. To overcome this, use your SCV to scout the opponent's unit-producing structure setup while continuing to train more SCVs. When you are at 12 cap, you should build your first Barracks.
3. Its time to build the Refinery when you reach around 15-16 cap. I recommend that you assign three SCVs to the Refinery.
4. You will need to build another Supply Depot when you reach 17 cap to cater for the upcoming units that you want to train. This will also add another blockage to your defense line that was built earlier with the Supply Depot and Barracks. After its completed, train your first Marine.
5. Before you train your second Marine, you should upgrade your Command Center with the Orbital Command. You should be around 19 cap at this time.

6. Finally, when you reach 20 cap, you will now build the Factory and shortly after that, you should follow-up the build with a Starport.
7. You can swap the Barracks with the Factory and produce Hellions. If done well, this can delay your enemies push quite effectively. At this point, if you feel like your opponent are preparing for a rush, you should swap you Barracks with your Factory instead and produce Hellions. This will help you to delay the incoming rush. Alternative, you can also use the Hellions to harass your opponent.
8. Later on, swap the Factory and the Barracks and get a Tech Lab for the Factory so that you can swap it later with the Starport.
9. Train a Raven and then build another Command Center.

10. Now the core buildings has been complete. You should proceed to build either Factories or Barracks, depending on what kind of combinations of unit you want to pursue. Its advisable to train units that can counter your opponent's game play.

If you want to learn more on what kind of units you should train so that you can create a combination to eliminate your opponents, I highly recommend the Shokz's Starcraft 2 mastery guide.