You really dont trade directly from other games. After you get the national dex, the palpark opens. There, you stick your older game into the GBA slot and visit the palpark where you transfer up to 6 pokemon a day into the palpark and out of your game. After that, its like the Safari zone without a time limit and a 100% catch rate.

Or atleast thats the gist of it.

Also, if you have former games, like Leaf green and ruby, inserting them in the second slot will bring other pokemon breeds into various areas in Diamond itself, so even if you didn't catch them in the original games, you have your shot now.

Hmmmm...i've got ruby and saphire, not sure how far i got on ruby, checking where i last saved, it looked like i was in a volcano, so might be just before meeting up with Groudon... Haven't really played saphire much, basically got it so could transfer out the starters and such :) guess it's time to hit the second hand stores and see if there are any copies of fire red, or leaf green...and mabey emerald as well....will have to see.
Anyway, so basically, your pokemon are pulled from earlier games and placed into D/P? so if you wanted to go back and play the earlier game from where you left off, you'd have lost whatever pokemon were transferred over, correct?

GryphRaptor