The achievements and trophies included in Portal 2 run the gamut of being frustratingly difficult to being easy as pie. Not cake, absolutely no references to cake here. Anyways, we have put together this handy guide with a whole batch of videos to help you get a complete list of accomplishments in both the single player and co-op campaigns.
For a more serene experience in acquiring the rewards found in the co-op campaign, you'll hopefully have a paitent buddy or else there may be some broken controllers in your near future. While not every achievement/trophy needs a video to show you how to get the goods, the more problematic of the bunch are here for your viewing pleasure. Enjoy!
NOTE: If you haven't played through it yet, please note that this guide contains POTENTIAL SPOILERS.
Bridge Over Troubling Water
Complete the first Hard Light Bridge Test
This will be gained in Chapter 3 while progressing through the storyline.
Examine all the vitrified test chamber doors
In Chapter 6 you will come to a high elevator shaft that you need to ride all the way up. Once you reach the top, you will need to portal over to the far right of the shaft where there is a catwalk and three doors. Listen to the three intercom panels in front of the doors and then continue on. The next three doors are located in the office buildings where you find the potato. In the top office that moves over, enter and in the far left corner will be a door behind a cabinet. Go through the secret door and there will be three more doors there with intercoms. Listen to them and the reward is all yours.
Place a cube on a button without touching the cube
In Chapter 2 test chamber 6, also known as the “Advanced Aerial Faith Plate Test Chamber” you will press a button to release a flow of trash and a cube. There is a pressure button on the left side that you need to drop the cube on to achieve this. Place a portal above the pressure button and on the higher angled platform and then release the cube. The cube will launch through the room and portals and land on the button.
Dual Pit Experiment
Do the same test twice
This will be gained in Chapter 8 while progressing through the storyline.
Find the hidden signal in one of the Rat Man's Dens
This is another achievement/trophy that you can get in Chapter 2, test chamber 6. When you press the button to release the cube, a bunch of trash will fall out including a radio. You want to grab the radio and then enter the opening to the right of the angled platforms. Once you grab the radio, toss a portal on the higher angled platform and one up high on the wall to the left of the angled platform, across from the opening. Head back to the beginning with the radio and then launch off the kicker and fly through, entering the office. Take the radio to the far end of the room and the transmission will begin.
Take GLaDOS' escape advice
During Chapter 4, you will start running with Wheatley along some catwalks and GLaDOS will tell you that you were almost done the tests. She will reveal one last test to the left with an exit door with plants in it. If you make your way over to it, you will receive this achievement/trophy.
That just happened
This will be gained in Chapter 9 while progressing through the storyline.