The Camera Shy achievement requires you to detach security cameras from the walls. Not all cameras can be detached, such as those on walls you can't place a portal on, and ones that appear before you have access to a portal gun, but there are 33 total cameras that you can detach. All you have to do is simply place a portal on the wall behind the camera, and if it has a corresponding portal of the other color, the camera will fall.
The walkthrough describes where the cameras are, while these screenshots display the cameras in context. Chambers not listed have no detachable cameras.
Note: skipping and re-playing chambers/levels will result in the counter for this achievement being reset. In order to complete this achievement do not skip any levels or miss any cameras on your first time through each chamber/level.