You need to transfer all 3 of the regis from you ruby,sapphire, or Emeralds game packs
sinnoh Pokemon won't appear in Sapphire version!
They appear after you captured or defeated Dialga/Palkia depending on your version.
In Pokemon Crystal Version, a Heracross will occasionally appear when you use headbutt on trees.
it makes wild Pokemon less likely to appear
Celebi does not appear in the gold or silver games, however he does appear in Pokemon crystal.
The point of the game is finding them yourself
Alamos Town does not appear in the Pokemon Diamond version of this game. It is in the movie, but not on this game.
Skitty does not appear in Rusturf Tunnel. Only Whismur are there.
Go to route 9 and catch it. It will sometimes appear.
Only Generation 1 Pokemon may be traded between Yellow & Silver. Note: The player using Silver version must only have Generation 1 Pokemon in his/her party and the Pokemon must have learned no moves that did not appear in the Yellow version. Also they mustn't be holding any items that didn't appear in the Yellow version.
Braviary (as well as it's pre-evolution, rufflet) does not appear in the wild in Pokemon Black version. You will have to trade with somebody who has Pokemon White version. Likewise, Vullaby and Mandibuzz can only be caught on Pokemon Black.
To release a Pokemon in Pokemon Diamond version you must deposit it in your PC and then click on it with your white arrow. Options should appear in a list, select "release" and then it will say: "Are you sure you want to release this Pokemon?" select "yes" and then...Bye Bye Pokemon!