When an Imp is going to through a fire-ball at you, just duck and it will miss every time. I know this is probably obvious but if you are right in front of a wall it will still hurt you but not as much.

Ok when you find the chicken punch game it should say out of order or somtin like dat crouch and go behind the machine and there should be a button press it and you will be able to play chicken punch!

When you get the chain saw not chainsaw gun the chain saw use only the chain saw unless it's like a huge monster or unless long rang trust me you will save alot of ammo

You can only get the rocket launcher and the bfg from them there is also alot of ammo.

Okay you must be on the last level to do this.

Okay I'm not that good at telling were this is but look every were in the ruins when you are near the last boss nthe cyberdemon.

It on the wall and it sould say Id and click on it then the wall shall open and the is the pda get it and look on you pda and the creaters of Doom will say thank you's...

You get it after you kill the guardian or at past the bridge in the 3rd level or

Go up to imps or zombies and when your like 50cm near then shhot and they'll die first shot.