1. Remove all the doors.
2. Remove the drawers.
3. Remove all internal fittings (shelves, rod(s), etc).
4. Remove any screws used to attach the frames to each other.
5. Remove any screws used to attach the frames to the wall.
6. Once you have the frames separated, move each one forward and carefully remove its back piece (I use a rubber mallet to separate the nailed back, going slowly in order to avoid damaging it).
7. After removing the back, you may want to lay each frame on the floor (face down) in order to release the cam locks to separate the top and bottom from the side pieces.
8. Repeat steps 6 and 7 for each frame.
It's a good idea to label each piece and keep all the corresponding hardware (screws, etc.) from each frame on a separate plastic bag. You should also take pictures between each step, so it will be easier to remember in case you need to reassemble them later.
I hope this makes sense to you.