While decker's tips are effective, the mass storage unit inventory micromanagement technique is not fun. That said... always have at least one container. If you lose it, shoot workers until you get another container. Without it you will eventually be overwhelmed when you lose some key part of your build (usually weapons).
It's totally luck based, or at least it appears to be.
I felt that way at first, but after playing awhile there are a few things I was doing that I didn't realize I was doing that got me in trouble early.
Hacking machines past detection. Once you are 'detected', move on. Even if you have a system shield and can easily get in five more attempts, don't, because each one will have a chance of raising the alert level.
Don't attack neutral robots ever, unless you have to. Especially engineers. If there is an engineer behind a robot you want to shoot or in the vicinity of a robot that you might accidentally hit due to a missed shot, reposition. I only attack haulers when I am in dire need of something, like a container or I have intel on what they are carrying. The same goes for machines, although destroying machines is a lot of fun, it drastically raises the alert level.
Get a move on. I could be wrong on this, but don't explore every nook and cranny of every room if you already have a sufficient loadout. The more time you spend on the level, the more robots will be walking around. Also, exits tend to be on the outskirts, so move away from large open areas.
Never run away from a patrol, unless you are really fast and they aren't. This is a stark contrast from dcss which is basically a sprinting simulation. Enemies will chase you and alert every other patrol in the areas you run through which alert more patrols. Soon you are trapped, weakened, in a dead end. You also risk running into traps which make everything worse. Exception: If a stream of robots is pouring from one direction, they might be coming from a garrison. In that case just run away for a little while. Even if you can kill stuff you are just escalating things and damaging your equipment for no gain.
Scouting is key. A basic visual processing unit can save you a lot of hassle. Don't always restrict yourself to hallways. Any non EM cannon and apparently most melee weapons can bite through walls, so always be looking for a shortcut between rooms where you are much less likely to meet resistance.
If you are getting shot to hell before -7, and you are pretty sure you won't make it, don't sit there futilely letting important equipment get shot off, just drop one by one, things you don't need and keep ones you do in your inventory. Try and keep a power source, a weapon, a propulsion, and a storage unit. Leave cpus in, they weigh nothing. Leave in something that weighs 3 or less, like a heat sink. Won't impede you and takes hits and could be useful later.
You already know that, but the reason I mention this is if you are at a high core integrity, it is almost impossible to lose in the first few levels unless you have a huge swarm of fast bots on your tail or a demolisher squad on top of you, because you can get away from almost anything, the stairs are always somewhere nearby, you can recover quickly on the next level if you have access to some basics. Failing all that you will usually find weapons and a choke spot somewhere, so just equip a couple of them and pick off robots that can keep up with you, then run again.
