StarCraft is partially a game of processing information.
Multitasking is one of the main skills you improve while playing.
First, you need to use hotkeys .
Use them to quickly get information on production status and jump to different groups.
With SC2, hotkeys can bind to multiple buildings or groups and you can use the Tab key to tab between them.
Personally, for Terran, 1 is for command centers, 2 is used for my initial initial scouting SCV and then for general unit usage, 3 is always barracks, 4 is always starports and factories.
5 through 8 become groups of units in the mid- and late-game.
The above scheme lets you tap 3 and 4 to see production status of the army.
Do this and, if you don't see white dots underneath the green building icon in the bottom console, start building something.
( What to build is another discussion.)
Cycle between your hotkeys to move units and check on production status.
Don't forget that double-tapping hotkeys takes you to the group, Ctrl and a number assigns the group, and Shift and a number adds units or buildings to the group.
Next, you really, really need to pay attention to audio cues in the game.
Make sure to turn the music off so you can hear them more clearly.
Finally, note that Space takes you to where the action is .
Did you year
"Our units are under attack?"
Hit space, and you'll be taken to the action.
Or maybe you'll remember which hotkey you assigned that group and you can double-tap it.
Hope that helps :)
gaming.stackexchange.com/users/1437/a paid nerd
There isn't a good answer for this
but I'll give you some of what I've found helps Don't focus on your army so much, when you send it out stay focused on your base When you're just about to make a push is a good time to expand (your opponent will be pushed back)
While you're in the middle of a battle build a couple workers.
New units usually won't get there in time (or you'll be capped on unit production), so its a good time to add in workers to rebuild after an assault (or defense).
Hot key your buildings, with Multiple Building Selection its really easy to have your production running from a distance
Make your pushes right after upgrades finish Always set your rally points, even if its just to the nearest choke.
I hope these help.
gaming.stackexchange.com/users/102/tzenes
In addition to most everything a paid nerd said, I would add a couple things.
Playing StarCraft well is similar to driving a car well.
You need to pay attention and check your mirrors a lot to ensure you're fully aware of everything that's going on.
With practice, you can get into a nice rhythm of checking on the fight, checking your building production, glancing at your base, and throwing up new buildings.
Specific things to watch out for: Are your workers idle?
There is an icon in the bottom left that pops up whenever that happens.
To help avoid them going idle, use Shift to queue up actions such as "Build a Factory, then go back to the minerals."
Are your buildings building units?
Do you have too many resources in the bank?
If you start to get high, you likely need to produce more, which may mean more production buildings.
Are you running low on supply?
Did you accidentally leave a bunch of units sitting next to your buildings?
gaming.stackexchange.com/users/32/Mag Roader
Have you tried getting gold medals in the single-player challenges?
They are designed to help you become a better starcraft player, and especially the last 3 challenges might be just the sort of practice you're looking for.
Unfortunately, the truth is that the only thing you can do to improve your macro (building economy + units is known as macro) is to KEEP PRACTICING! :)
gaming.stackexchange.com/users/336/Raven Dreamer
Just to add a little to a paid nerds' excellent answer: learning all the hotkeys, for building various units is also very important.
So you can be in the middle of a fight, quickly tap you
barracks shortcut key, crank out a few more units by bashing A (marine) and D (marauder), then tap your units short cut key
and you're back in the fight!
In all, even without practice, that's ultra fast.
Getting the hang of this was a bit of an eureka moment for me.
gaming.stackexchange.com/users/2440/Geoff
If you want to improve your multitasking, the best way, is practice.
For good practice, I recommend giving the "multitasking trainer" map a try.
http://www.sc2mapster.com/maps/multitasking-trainer/
gaming.stackexchange.com/users/1919/rysama
There is the grid option in hotkeys which helps a lot (especially on my ergonomic keyboard)
What does Grid do
When you select Grid every button in the Bottom Right is assigned to match the following layout q w e r ta s d f gz
x c v b
For example: if you're in your hq press q to build scv or if you have units selected use t for attack-walk (don't remember the correct name)
gaming.stackexchange.com/users/2128/peter
I feel like my main deficiency is that I have a hard time with the multitasking required.  Specifically, when I have troops in the field, especially more than one group of units, I tend to not keep up with building (structures and units) and my resources just sit there, wasted.  What strategies can I use to keep up with building structures and units while I'm coordinating my troops across the map?
How do I build and fight simultaneously?
gaming.stackexchange.com
<starcraft-2>
gaming.stackexchange.com/questions/4732
gaming.stackexchange.com/users/816/sjohnston
Use hotkeys and multiple building selection to have your production running from a distance. You should also be paying attention to audio cues. While practice does play an important role in this, there are some things you can do to get better at this. Chief among these is to set and learn some hotkeys. Paying attention to audio cues, and idle workers is important, as is timing things correctly.
Setting and learning hotkeys is important. While practice plays a role. Users also warn to pay attention to the audio cues. Timing is also important. Watch out for idle workers.