"Not getting to grips with the game's mechanics."
Of all the things that would cause me to lose the most, that one above would probably be at the top of my list, especially as a newbie to the game. Sure, rts games in general aren't exactly easy to just pick up and play for a newbie to the genre, but deep and complex rts games like Supreme Commander and Zero-K are especially prone to this.
Other common ways for newbies to lose (imo):
- Lacking in attentiveness, which rts games in general are notorious for demanding out of players, which can result in all manner of mistakes, like these below:
[Spoiler]--- Failing a spot check against a sneak attack, most likely because your attention was focused elsewhere (such as on the frontlines, or exploring or base construction because you forgot to build a radar).
[Spoiler]--- Forgetting to manage and balance your economy in some way, such as failing to assign new orders for idle builders or factories (setting factories on repeat helps prevent that), or failing to construct additional caretakers to counteract metal gluts, or failing to construct additional energy buildings to counteract energy shortages (which could also result in metal gluts that cannot be mitigated by increasing buildpower, since buildpower requires extra energy as well as metal). To keep myself from making these kinds of mistakes, I've developed a habit of always trying to have more active buildpower (such as from building units from factories set to repeat build) than metal production from mexes, and always trying to have more energy production than buildpower (in case I need to spend energy for special abilities like cloaking or shields). In the early game, I have a habit of building lines of wind turbines from mex to mex.
[Spoiler]--- Forgetting to take advantage of reclaim. Admittedly, this is something that I'm still struggling to find a way to manage with little effort on my part. Perhaps I could set patrol routes for fast constructors (such as a Crane or Athena), so that they would passively look for reclaim near locations where I've repelled enemy attacks. I'd also need additional caretakers to manage the additional metal influx.
[Spoiler]--- Forgetting that you aren't limited to just one factory. For example, are Moderators, Phantoms, Racketeers, and/or Lances giving your heavy tanks, including your Blitzes, Kodachis, and Minotaurs, a bad time? Try building a factory that will let you build cheaper, more expendable scouts or raiders, such as Fleas, Darts, Puppies, Glaives, Bandits, or Daggers, to overwhelm the enemy units, whose firepower would be overkill for the cheaper units.
[Spoiler]--- Forgetting to expand and claim new mexes during a heated battle. Sure, the heat of the battle could sap your attention, but don't forget to continue developing your economy. Admittedly, this is another problem that I need to work on, but I've recently developed a habit of queuing long build orders of spaced-out Fusion Power Plants and Singularity Reactors near the safest parts of my base (and away from anything important), usually the back. However, I still need to get into the habit of occasionally sending a constructor out to claim new mexes.
- Overestimating/Underestimating your capabilities in some way. (In other words, failing to know yourself from Sun Tzu's "The Art of War".) Some examples of this include:
[Spoiler]--- Being overeager to attack without knowing your opponent's capabilities, which could mean that your forces get stomped hard, and the reclaim is stuck within enemy territory. Creeping up with radar towers, or even advanced radar, should help give your forces a bit more info on where to best attack.
[Spoiler]--- Being overeager to expand and claim additional mexes. Without the energy and buildpower to spend it all, that additional metal income is pretty much meaningless, as you're just wasting it. Moreover, even if you do have the energy and buildpower to spend all of that metal, the enemy can and will attempt to sabotage your economic assets wherever and whenever possible, especially if said economic assets are poorly-defended.
[Spoiler]--- Being less than eager to harass the enemy. While the enemy might scare you with a sudden attack that you were barely able to fend off, chances are that, if the attack happened early, the enemy might be vulnerable themselves. Remember that the enemy might be trying to distract you from the bigger battle with small probing raids that might distract your builders and commander from doing more important tasks. Building radar early should help you spot enemy attacks in advance, which you could then intercept with whatever forces you have available.