Start Ruby up in the Main Menu.Now go into the nearest Pokemon center, and make sure all of the 6 Pokemon you wish to migrate are in the PC (you can only migrate 6 Pokemon at a time to Diamond once a day; you may want to put these 6 Pokemon into their own box for an easier time) Save the game, and turn off the system. Turn the DS back on, and choose to play Diamond(if you have your system on auto-setup, just turn on the power). Go to the screen where your game options are offered (continue game, new game, WI-FI options, etc.), and choose the "migrate from Ruby" (don't try to migrate until after I beat it, I don't know if the migrating thing is avalible throughout the game, or only after you beat it... sorry). Read all of what the game has to say, and choose the pokemon you want to migrate (if both games don't have the same exact time, you'll have to wait another day to migrate). another day to migrate). Catch your Pokemon @ the park made just for doing so (just go DOWN from your hometown, Twinleaf. You'll need to know surf and cut, I believe. After finding it, you can just fly to it. Be sure to have some strong Pokemon in your party... there are some trainers to battle, as well as some-times- rare pokemon to catch)