Yes, you can, but only to another Pokemon Black/White ROM, and only once you have obtained 2 Pokemon( that way, you can never have no Pokemon). You can probably use the Union Room in the next town with a Pokemon center. You can also trade from your other games, sort of like the Migration System in DPP, But its not exactly the same. And once you trade your DPP Pokemon in B/W, you can never trade them back.
you can trade pokemon from heartgold to black but you can only transfer the pokemon in heartgold not trade it from black
No, but you can trade Pokemon only in HeartGold to Black
there is no way you can trade mail on pokemon black
You cant trade pokemon soul sliver to black or any game you could only trade black to black or white to black
no you can trade soulsilver pokemon to black
Zekrom is NOT in Pokemon Black. You have to trade it from Pokemon White.
Pokemon White, and other copies of Pokemon Black.
No. Just like in Pokemon Pearl with the Pal Park you can only trade from Pokemon pearl to black, not back
No you can't trade with black to diamond but you can trade from diamond to black using the poketransfer lab. (you will have to have beaten the game before you can use the poketransfer lab). Hope I helped this is luke127 signing off.
at the pokemon center
You'll have to transfer it into Pokemon Black or trade for it.
no but you can trade Pokemon holding the items.