-You can NOT kill the Alien [Period]
-The Alien will kill other humans but not synthetics.
-The Alien, other AI, and type or number of items will not spawn in the same place each time the game loads.
-You get a current save point, a previous save point, and a mission save. That's it.
-The Alien can hear you running.
-It can run WAY faster then you.
-The Alien can hear your motion tracker, even in lockers.
-You can carry extra items by committing parts to items but not completing them. You can add binding compound to Medkit if your compound is maxed out buy leave out the injector if you only have a few. That way you leave supplies behind and don't lose the option to apply the injector to something else you may need on the fly.
-Equipping the Molotov or aim the flame thrower are an unlimited source of light in dark vents.
-Synthetics can't follow you into vents.
-Just because your in an interface, PC, junction box, or save terminal doesn't mean the enemy will pause, make sure the coast is clear before using them.
-Flares are the cheapest tool to distract with. You can't make them, but given how much attention the bring, you won't use them a lot if at all. So use them to set traps for the Alien. Place a flare next to a Molotov. This is especially good if you know you will have to back track through an area.
-Humans can be killed easily, but many are armed and starting a gun fight will attract the Alien.
-The stun baton can kill a human instantly and quietly. It can also disable a synthetic that's not wearing a hazmat suit. You can then finish them off with melee attacks. But watch out activity often gets the aliens attention.
-Noise makers will get the Aliens attention the first few times, but it will stop going to them if you use them to often. It will know someone is around.
-The flame thrower can be used to scare the Alien back into the vent. But it won't stay away for long. And it will become more and more brave. An issue considering the scarcity of fuel. Some missions, the alien will get frustrated trying to find you and hop back into the vents until it hears activity again.
-Careful walking under air vents in the ceiling. Sometimes the Alien can be heard in the vent and drool will drip down, other times you happen to be in the wrong place and the wrong time.
-Corner the Alien with the flame thrower and it will push it's way passed you deal 50% damage. Use to too late and it won't even matter.
-Facehugger are an instant death. You can melee them every time because of an auto lock but it will deal 10% damage.
-When you get to the hive, there's more then one Alien, save often.
-Your going to find more parts to make a Molotov then our are flame thrower ammo and the flame thrower doesn't scare off the Alien right away.
-You can get one melee hit on a synthetic before they grab you. Hit and back off, then strike again. Or disable them with an EMP or flash bang then beat the piss out of them.
-Synthetics don't run, but like most slasher films they always seem to catch the victim, plan accordingly.
-Just because a synthetic is down on the ground doesn't mean it's dead.