you go to the trading center with both games and trade them :)
No, but you can transfer/trade Pokemon from Diamond to White.
Transfer it from Diamond.
To transfer your Pokemon from diamond to white you first have to beat the game in Pokemon white. After that you have to go to the Pokemon transfer lab, go up the steps and speak to the scientist. Then you need another DS that has your Diamond Pokemon in it, go to DS download play on the main screen and you can choose six Pokemon to transfer from your storage. 1) You must have already beat the Pokemon White Game 2) You need 2 DS's 3)The Pokemon that you want to send to Pokemon White must be in your storage in the Pokemon center in Diamond.
I'm not that sure if you can trade, but you can transfer.
transfer from diamond, pearl or platinum
Yes, assuming the games in the consoles are compatible versions, it doesn't matter which console they are in. For example Pokemon Diamond in a DS can transfer to Pearl in a DSi, and vice versa. But while you could transfer from Diamond to White with either, you could not transfer from White to Diamond.
just transfer it from pokemon diamond,pearl or platinum
If you have Celebi on Pokemon Diamond, Pearl, Platinum, HeartGold, or SoulSilver, you can use the PokeTransfer machine in Pokemon Black and White to transfer it.
You can't, you can only use poke transfer to transfer up generations not down.
You are unable to transfer Pokemon to previous generations, mainly because there are all new Pokemon in Black and White.
if you are asking if you transfer Pokemon from HG/SS/Platinum/Pearl/Diamond to Pokemon black and white will they be gone from HG/SS/Platinum/Pearl/Diamond then the answer is yes.
You can't, you can only get Giratina in Pokemon Diamond, Pearl, or Platinum. Then you transfer it over to White.