White Version: How to Get Arceus

ATTENTION! This only works till 1st of March 2012 on Black/White Version!

DS 1.1.: Go to Online - Game Sync and tuck in a Pokemon from your box. It does not matter which Pokemon you use.

Computer 2.1.: Go to Pokemon Global Link (http://en.pokemon-gl.com/) Sign in your game.
Computer 2.2.: Go to Promotions and click Receive The Mythical Pokemon Arceus.
Computer 2.3.: Write in a code ARCEUSVOTE
Computer 2.4.: Go to Pokemon Dream World. Now you will see the Pokemon you tucked in.
Computer 2.5.: Go inside the house by clicking the door. Inside there is a board on the wall. Click it.
Computer 2.6.: You will see Pokemons that have visited you. There should be a picture of Arceus. If not, do this again on the next day.
Computer 2.7.: Leave Pokemon Dream World by click a button on the screen that looks like a off button on the computer. Choose to wake up your Pokemon when you leave.

DS 3.1.: Go to Online - Game Sync to get your tucked in Pokemon back.
DS 3.2.: Go to Wireless - Entralink
DS 3.3.: Now you're in the Entra forest. Walk up to the forest. Do this till you can't go further. In the last forest room Arceus should be waiting for you. If you can't find Arceus, try this again on another day. You don't need to battle Arceus, just throw any pokeball you desire to capture it.

                                  Crappy picture I took of my encounter with Arceus.