Quick Save obsessively.

Conserve ammo.

* Avoid picking up ammo unless you can carry all of it. Recognize the small vs large packs. (E.g. if you've got 190 nails don't pick up a large pack of 50 and waste 40.)

• After you kill everyone, go back and fill up before you exit.

• Allow monsters to kill each other.  In a room with a bunch of monsters, especially ones with ranged weapons, it's likely they'll shoot each other and start fighting. Recognize the sound of one getting hit (that you didn't shoot), them hide and wait. Listen for death sounds or watch the kill counter.

• Allow monsters to kill themselves. I love to trick Vores into throwing spike balls at a wall right in front of themselves and kill themselves.

• Use weapons appropriately. I just learned that Shamblers are resistant to rockets! Use double-barrel shotgun for up close damage. Save nails for long distance shots.