In Chapter 5 'The Escape' reach the conveyor belts carrying droids to the incinerator and use a portal to get onto the conveyor belt. Then walk on the belt until a droid with a working laser beam appears. When you pick it up you will get the Achievement.
When you attempt to earn the 'Ship Overboard' Achievement and you enter the door behind the filing cabinet there will be three metal doors in the hallway. Activate ALL 3 doors and Cave Johnson will talk about the tests and you will get the Achievement.
In Chapter 9 after Wheatley's surprise, portal away from the platform just as Wheatley sends arms to crush you (Don't run away on the catwalk). Stay nearby and Wheatly will beg you to come back. Stand at the edge of the pit overlooking his trap and jump in when he asks you to and you will earn the Achievement.