FIRST you get a ditto and a Pokemon that knows thief go into double battle in Pokemon tower(north from fight zone) and have thief as first Pokemon and ditto second(so they both go first) make your thief Pokemon uses thief them make your ditto transform and win the batlle the retire and save then you have the theived item twice unfortunetly this doesn't work with your items in your bag BYE BYE. =)
To multiply items on Pokemon Diamond/Pearl, you need the action replay. Unfortunately, if you have the DSi, the action replay won't work. It only works for the DS. If you want to 'multiply' Pokemon, breed them by leaving a male and female Pokemon in Solocean Town Daycare Center. Possibly, they could lay an egg!
You can't store items on Pokemon Diamond and Pearl, as your bag now can carry an unlimited supply of items.
Get action replay.
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!