Doom/E3M8: Dis

If you collected the BFG on a previous map, rush the Spider demon with that weapon - it will fall in only two hits.

Otherwise, you will want to run to the left and collect the rockets and cells. While you can defeat it with the just the weapons and ammo available on the map, or even just the monsters themselves, there is almost no room for error.

Once you collected the first batch of rockets, run to the center and open the door. Pickup the Plasma gun and blue armor, and destroy the spider demon.

Secrets
There are no secrets on the map. However, you can open the middle section for a plasma gun and blue armor.

Deathmatch
This map isn't designed for deathmatch. There are only the two weapons, and a single blue armor in the middle.