I would imagine the response depends on the specific situtaiton; why are you cleaning them for exactly? What are you trying to accomplish (i.e. simple cleaning or polishing?)
If it's just simply dust, a very fine fabric, such as glasses cleaning cloths or a plush microfiber would do nicely.
If there are stains, you can dab a cloth (again, a scratch-free fabric is always best) in some water and just remove the stains as such.
If it's something more, then you're going to have to take into account certain things..like is the headphone raw metal or is there a clear coat. Same with the pad..is is faux leather or genuine. Then you can start picking your cleaning solutions. Never start with a strong chemical solution, start weak and work you're way up.
EDIT:
If you want to clean specific parts without removing parts, a good idea is to mask them off using a non-scratch masking tape. I believe 3M has such a product that was created for car detailers so that the masking tape would not scratch the car
Hope this helps
