Well, when facing androids, don't move to fast at them because they have better senses then humans, you'll have to move real slow if you're trying to sneak kill them and the plasma caster when used at full power can obliterate one human and knock down anyone near him so thats useful for if you can't get them to seperate. And remember, darkness is the ally of the xenomorph so if you can, try to stay in the shadows. And as a marine, don't panic becuz then everys sound will make you jump but be prepared for anything, the marine does face the most dangers.