But with so much open doors and such fast aliens, that is rather hard, especially in lowlight areas.
You can close doors with the 'act' command. (I think it's the spacebar by default?) This alone helps a ton by avoiding unhealthy situations.
In a game like AliensRL, managing your ammo is crucial. You're not guaranteed to get a lot of it wherever you go, and certain towers have more of a given type than others. With this in mind, who you decide to fight is of utmost importance (since you want to get enough points in the weapon skills to actually make good use of them): the biggest bang for your buck are hunters, since they're only slightly more durable than juevenilles. You can usually find a lot of them lurking in the hallways, where they're far easier to kill without getting attacked. Drones and workers (and, when you find them, overseers) aren't worth the trouble due to their really high armor and HP. I find that, if you're low on ammo, you want to descend a little to somewhere you haven't been and search around. You can build up a hefty surplus when things die a lot faster (as a result of improving your skills).
Weapon-wise, I find that sticking with the starting pistol and leveling your sidearm skill to at LEAST advanced ensures you a good killing weapon at a distance. The other two sidearms are much harder to find and only one is actually worth finding, but comes with the trouble of having pretty rare ammo. Pretty much all of the primary weapons are good (for when you find them): combat shotguns have the unfortunate side effect of hitting enemies you don't want to hit (like workers), making a bad situation even worse; SMG is a great way to kill fast but eats through your pistol ammo faster; the other ones are almost always superior. Heavy weapons are...well, really strong, but difficult to manage: they don't matter until end-game and you won't need one to win. Really, if you get in a tough situation, that's the time to throw some grenades.
The rest is just technique, which is summed up quite nicely by Jo's link.
EDIT: I actually have a couple of (successful) video playthroughs recorded on my channel: one by a Scout and one by a Medic. The latter completely surprised me, as I managed it on the first attempt (well, first recorded attempt). Check my LP thread for the link.
