Enemies are tough, and ammo will be limited at the beginning: you start off with an automated sentry gun which can be deployed and picked up again at any time, and is a life-saver on several occasions. In fact there will be times were you are a goner without it.
Remember that your starting weapon (pistol) has a flashlight so you may need to switch back and forth a lot. Also, you have a supply of flares for lighting up areas or simply marking routes.
Aliens have acid blood: remember that before shooting one point blank in the face with a shotgun!
Just the wads version (load order is D3tex.wad, AEM.wad, AEM_Mapset.wad):
Grab It Here
p.s. I don't need any feedback about the maps themselves since they are just quick and dirty with numerous issues.