The level begins in a laboratory area, where Compilers are performing hideous experiments on trapped Bobs. These fights are tricky since the seeking bolts are very hard to dodge in that sort of layout, so it's usually better to bring out a rapid-fire weapon and go toe-to-toe with them in the corridors. You can even use your fist if you're low on ammo, but be careful to make your stand at a spot where only one compiler can reach you at once.
I chose to scour the rest of the level before taking on the big fights leading to the boos, since on my first attempt I survived with very little health and got killed by a Fighter, of all things :\. The level is quite interconnected, with passageways and teleporters everywhere. Heading down the secret door opposite the entrance to the southernmost Compiler lab will lead you to the same spot that jumping down to the teleporter in the center will.
When fighting Enforcers, take advantage of the fact that in Marathon 1, unique among the games, they are willing to chase you. In Marathon 2 and Infinity, Enforcers tend to hang back and wait for you to come to them once they find a good spot. Also, note that going through the level backwards as I have done negates a number of small ambushes placed throughout the passageways; you often come upon fighters from behind as they wait for you.
At the very bottom of the level is a secret infravision biobus chip, one of only two in the single-player game. It doesn't really make things easier, the level isn't that dark. But if you pick it up you will probably notice that it has several drawbacks that may not have been noticable the first time you had one. The Compilers are mostly immune to its sensors, they are drawn blue as part of the environment. Also, the rank of enemies is disguised, you can't tell if that fighter charging you is a puny Green or a (slightly) more dangerous Blue.
A number of tricks can make the attack smoother. Firstly, the ambush in the approach corridor can be avoided (or at least made far easier to deal with) by opening the first door manually and filling the room with burning napalm, removing any monsters that would have come up behind you. Secondly, taking out the monsters in the cyborg's room itself if easy: Run off the ledge backwards and launch a rocket straight down (be careful not to pass over or land in the slime pools). As has been noted many times, the cyborg itself is quite weak, taking a few shots from the pistol to explode.
The teleporter at the bottom of the main lift has an interesting quirk: There are two invisible compilers incorrectly placed on the map so as to be overlapping and trapped in place.
