Trade in battle points at the battle frontier.
You can't store items on Pokemon Diamond and Pearl, as your bag now can carry an unlimited supply of items.
the power items are power anklet, power lens, power bracer, power weight, power band and power belt, they help speed up the process of ev training and can be obtained at the battle tower for 16BP each
Use items or go to a Pokemon Center to heal your Pokemon.
somehow
you are unable to send any items from the past games to pokemon black/ white
You can't rotate items. They stay in the direction you get them in.
Some hidden items are in the Safari Zone as well as some Pokemon.
sooth bell
face it and press A
Go on to Google and put in Pokemon diamond walkthrough. it gives you a step by step guide and shows where items are and what they are!
You cannot clone Pokemon and items on diamond and pearl and platinum, but you can in emerald!
Action Replay. That is the only way that I know of.