How can I make duplicates of an object using empties as placeholders? For example I have a cube as original. After that I place some empties with a certain position, rotation and scaling and then turn those empties into duplicates of the original cube?
First select the cube and create a group Ctrl + G
Then select all your empties and go to the
Properties Panel >
Group and then choose the newly created group from the dropdown.
If you have selected more than one empty, hit Ctrl + L with all of them selected and click on
DupliGroup to have the Group property copied to all of them.