NiCd`s are rough gadgets. As already stated they can be stored full or empty and still be brought back to life after a long while.
But the "recommended" way to do it is to discharge NiCd before storing. NiMH should be partial discharged before storing.

NiCd and especially NiMH should be waked up from storing in the same way as you threat new batteries. A slow charge at 1/10C for 14 hours. Then a discharge to check capacity. If the capacity is good charge in a normal way, with peak detect, and go flying. If the capacity was lower than expected run the battery through 2-3 charge/discharge cycles. If the batteries are healty their capacity should increase up to expected level.
NiCd usually responds good to 1-2 wakeup cycles. NiMH might need 5 cycles. Especially the high-current NiMH`s.