OMG I stink at this game

Never played the first SC and have just played Supreme Commander/FA to death the past few years.
Can anybody give me some basic pointers? With Terran I get slaughtered by the AI on easy. I pump out a few units as fast I can, but the first enemy attack kills them easily and then it's game over within 5 mins
I seem to have had most success with Zerg - I actually manage to inflict some damage with them. Terran just seem so weak and I get absolutely destroyed in no time. What am I doing wrong?
I don't even know where to start with Protos - LOL
Before the beta of SC2, the most i'd really played of strategy games was C&C/Total Annihilation/Supreme Commander/Star Trek Armada sort of stuff on the most basic Single Player level. It's very possible to learn starcraft 2 though and get reasonably good at it without having experience in the original or Warcraft.
I'm writing this bit having written everything below. A lot of this may come across as patronising if you already know it, so please dont take it that way. I sorta ended up brain-dumping to some extent here. If you already know what i'm saying here then great, otherwise hopefully some of it will be useful

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To be honest, the most useful stuff to think about is the economy stuff. The first part of what's below and effectively scott's entire post. Later on, when you have an idea of what race or races you'd like to work with more, then the race-specific stuff will become more important. Might be an interesting read for now, but the most important thing is working on getting used to the mechanics and getting your economy up and running.
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w.r.t. economy, what scott said for the most part really. The best way to improve is to start with the fundamentals of economy management. How are you going to get money? Then how are you going to be spending it?
How you get money: as scott says, by making workers. always. Even when your mineral line and gas are saturated, it's still worth making workers as once you get an expansion up, you need workers to mine. So why not have them ready immediately

. Building upon this concept is each race's 'macro mechanic'. Zerg have larva vomit, Protoss have chronoboost, and Terrans have mules. You want to get into the rhythm of using these. Chronoboost is a bit more dynamic, but with zerg you want to
always be spawning larva. The higher the energy on your queen, the more potential larva that you could have. So if your queen's energy is low, you know you're doing well

. Similarly, Terran should always be able to keep a mule on the field with their orbital command. So you can watch for when your OC hits 50 energy. Spawning larva efficiently will make a big difference to your drone count and ultimately your resources as a whole. Similarly, mules are essential for Terrans to keep up with the capability of protoss and zerg to get workers out fast.
How you spend money: With unit producing structures! For the most part I would say build the units you like. If you like marines, then by all means build marines! The most important thing about this side of your economy management is spending as much of your money as possible. It's great to have 2000 minerals and 2000 gas in the bank, but that's potentially 13 zealots and 13 high templar. That's 52 supply-worth of food right there! So the important things to think about, again as scott says, are always building units out of your structures, and making sure you dont get supply blocked (i.e. when you cant build more units or workers for want of more overlords/supply depots/pylons).
Mid-game to Late-game considerations: Ok, so we've got our marine-marauder/roach-hydra/stalker-colossus ball growing and we're feeling good. What next? The first thing to mention is upgrades. Never, ever neglect upgrades. +1 to armour or weapons may not sound like much, but it can make a huge difference. For example, +1 attack zealots can kill base zerglings in 2 hits rather than 3. That's a huge decrease when you consider a huge ling vs zealot battle! Also, 3-3 upgraded marines and marauders are beastly. The second thing to think about is continuing to expand. At some point, your main is going to be mined out, so if you're going for the late game, plan to take a third at some point. Otherwise you'll end up running out of resources, unable to produce out of your 2-base structures

.
There's so much to say, but these are your basic economic concerns, most of which can be summed up by what scott said. If you can get your head around just these concepts, then you're doing
very well in starcraft 2 terms

.
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Some race specific pointers in 1v1 laddering:
I'm not sure whether to delete this section, it's very incomplete and i'd like to add a lot to it. But, I've written it now, so I might as well keep it in. If you're interested I can make some replays of some of the basic builds being done vs an AI or human opponent and post them online.
Zerg - Ok, so we're the swarm today. Recall earlier I mentioned spawning larva. Larva are just as much of a resource for us now as minerals or gas. The more larva we have, the more units we can make. And boy do we want to make a lot of units

. If we dont have enough larva, we wont be able to spend all of our money, thus wasting potential army size. Zerg are perhaps the most dynamic race in starcraft in that they can be the most aggressive or the most passive. You can either have the strongest macro game, building drones faster than any other race can build their own workers, or you can take that same inherent capacity and push it 100% to units. There's even a middle ground there of some units and some drones. This gives you quite a lot of room to work with in specialising your build. Generally, in a macro game, your focus is on building drones. Get as many out as you possibly can and saturate your bases as quickly as possible. The trick in this is to not immediately die while trying to do so. That's where building units comes in.
On the flipside, you can be incredibly aggressive with zerg. Builds such as the 7 roach rush, 8 pool, 2 hatch mass lings.. (dare I say 6 pool) can be incredibly powerful, and shouldnt necessarily be overlooked (other people will certainly do them to you).
For a basic "safe" macro build, I would suggest starting with something like the following:
9 overlord (i.e. overlord immediately when you have 9 supply and 100 minerals)
14 gas
14 spawning pool
Mine 100 gas out of the geyser
15 overlord
Research metabolic boost and build a queen once the pool finishes
This is an excellent way of building lots of drones and getting reasonably fast zergling speed. This allows you map control very early on, and you can use the zerglings to scout your opponent's base and pick off stray workers or units. It also gives you about 300 minerals at around 21/22 food, allowing you a relatively safe expansion.
There are some incredibly good zerg players on this forum, much more talented and experienced than I am, and I'm sure they'd be happy to help you work with the race

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Terran - Ok, so today we're terran. You have so many options to work with, but our priority in general is to get an orbital command up reasonably quickly so we can start calling down mules. In terms of units, Terran has arguably the best selection of the lot, with units well specialised for different tasks. For example, hellions which excel at killing light units (such as workers!), especially with the infernal preigniter upgrade. Also the ghost, which can emp Protoss shields, effectively dealing 40-100 damage to every single unit in the emp's radius. You also have at your disposal the siege tank, sporting the longest range of any unit in the game. Finally you have the marine, which is just good at...everything.
There are many possible openings for terran, but most of them start out pretty similarly:
10 supply depot
12 barracks
13 gas
Orbital command upgrade as soon as barracks finishes (should be after the 15th scv finishes, so at 15 supply), also start a marine.
There are variations, such as building 2 barracks, one at 12, one at 14 supply. This allow for lots of fast marines to put early pressure on a zerg player, for example.
Once you get to this stage, however, things start to diverge dependent on what you want to do. Do you want a factory to get some tanks/hellions/thors or to tech up to a starport for medivacs/vikings/banshees? Or do you want more barracks to get a heavy marine/marauder force? That's down to preference. What units do you want to make?
In terms of unit choice, a common strategy is to go heavy on marines vs zerg, with tank and (later on) thor support. Against protoss, a fairly even marine/marauder force is often preferred. Marauders are incredibly good at taking on small numbers of protoss units in general and they rip through stalkers in a big battle. Marines, as always, are fantastic, mobile damage dealers so find a place in pretty much any terran force.
One thing to be wary of as terran is getting stuck on very few bases. Terrans have an advantage in that mules allow them to gain more income per minute from a single saturated base than any other race. This means, however, they they will mine out a base faster. Don't get stuck with no minerals left!
Again, some excellent Terran players on the forum, who I'm sure will be happy to advise much more specifically and in depth than i have.
Protoss - The forces of Aiur. Ok, so protoss. You say you don't know where to start so let's start at the very beginning, the nexus. In other words, let's talk about chronoboost. Just as zerg has the ability to use spawn larva to greatly enhance both or either their drone count or unit count, protoss can use chronoboost on the nexus (to build more probes faster) or on their unit producing structures. So you can accelerate the production of that all important zealot to hold off the 6 pool, or abuse the chronoboosting power of two nexuses from a fast expansion to outmacro a zerg opponent.
The principles for playing are the same as with any other race. Always produce probes, always produce out of your unit producing structures, and try to use your macro ability as much as possible. So try to use the energy on those nexuses anywhere you can (upgrades at a forge are a good sink for chronoboost).
So what structures should you be getting? I will suggest a strong PvZ strategy to get you started.
PvZ - 3 gate expand
9 pylon
chronoboost probes as soon as pylon finishes, should be able to put down a second chronoboost as soon as the first chrono finishes.
13 gate
14 assimilator
chronoboost when possible on the 15th probe
16 pylon
Build a cybernetics core as soon as the gateway finishes (should be approx 18 supply).
Start building a zealot and build 2nd assimilator as soon as probe production allows.
Build next pylon when probe production allows. Also start warp gate as soon as core finishes.
Add on two more gateways.
The idea of this is to have 1-2 zealots and lots of sentries before expanding. This allows you to be incredibly safe at any choke point you can find. As you're building sentries, you'll note your minerals getting higher. When you reach 400, that's your cue to expand. The huge advantage of this build is the ability to put pressure on your opponent at the same time you're expanding, giving you a very safe avenue into the mid-game. You can push into a zerg opponent's fast expansion while your own is building and potentially do a lot of damage (or at least make them build units rather than drones for a bit).
Protoss can be a lot like zerg in that you want to get used to gateway timings. Production cycles can align, so all you need to worry about with warp gates is remembering to hit your preferred hotkey (w will go to warp gates, or you can assign them to your own numbered hotkey) and warp in once the cycle is ready.
In terms of building numbers, the general guide is: 3 structures per base for normal production, 4 for an all-in.
So for example, with 4 warp gates, I can't hope to make units out of all of those and build probes and pylons. So unless I win then and there, or at least do significant damage to their economy, my economy will fall behind. A more stable long run strategy would be to produce out of 3 gateways for example.
Once again, there are some great protoss players on the forum, who i'm sure would be more than happy to give more detailed help and advice.
My final pointer would be to post replays on here, post about troubles or just amazing games you've had and talk to people ingame. I'm generally in the "OcUK" chat channel whenever i'm online. The best way to get good at Starcraft 2 is with other people, not on your own

. Feel free to add me in-game on VoidPtr.167.
Blimey this is a long post
P.S. Don't be afraid of the practice league in multiplayer! It's a great way to play around with the units against a real-life opponent in a situation where there's no pressure to win for the sake of league standing or anything like that. Just go on, play some games and have fun!
