The second mission contains a shout-out to the film Blade Runner, as foil unicorns are scattered around that area of Sevastopol station.
The "Stunned" trophy/achievement requires you to use a non-lethal attack to knock down either a human or an android. For a human, you'll want to use a flashbang. The blueprint is in the same room as the data cell in the third mission. For an android, you'll want to use an EMP mine. The blueprint is in the adjacent room to where you get in touch with your team in the fourth mission. For either item, collect the materials required to build it and then throw it at a human/android.
Easy "Mind Your Step"
The "Mind Your Step" trophy/achievement requires you to get through the Reactor Maintenance section of the 14th mission without dying. Some players have found it useful to use a USB drive or other backup method to make a copy of the auto-save when they enter Reactor Maintenance, so they can restart from that point instead of the mission's beginning if they die. The flamethrower is vital here. Use it against the spiders as well as the Spider Pods.
Easy "Just Out of Reach"
The "Just Out of Reach" trophy/achievement requires you to get through the fourth mission without fighting the androids - fighting or being killed by the Alien won't stop you from getting this). Do not attack them. Avoid running, and crouch when necessary to make less noise. If a hostile android spots you, run and hide. If one makes contact with you, you should restart.
Easy "Run Hide Survive"
The "Hide. Run. Survive" trophy/achievement requires you to get through the fifth mission without being killed by the Alien. You won't be in danger until it comes down from the vents. From that point on, you should avoid running. Crouch when necessary to make even less noise. You need to pick up a keycard from the corpse in Room A-29. Keep the motion tracker handy to make sure the Alien isn't too close. After you get the keycard, you just need to escape the area. You should restart if the Alien spots you.
Easy "My Turn Now"
The "My Turn Now" trophy/achievement requires you to use only the maintenance jack to kill an android. An easy way to do this is to sneak up on the friendly one at the very start of the fourth mission, hit him from behind, run away, and return to hit him again once he's lost interest.
Camping Alien Glitch
Sometimes, if you are hiding in a locker, the Alien will stop directly outside the locker and stay there. It won't walk around but it will continue to do that characteristic Alien wiggle directly in front of the locker. Wait as long as you like, the Alien won't leave. The only thing you can do is to exit the locker. Generally the Alien will continue on about it's business without attacking, but not always.