To get a full National Pokedex, You need to use the Action Replay Chip thingy... I did it! It's really ez X-cept for getting the code because some people lie about the numbers on the code... >:(
You will encounter Prof.Oak in Prof.Rowan's Lab and you will receive Poke Radar and Prof.Oak will ask you to come to the Pal Park where he will give you a National Pokedex.
get an action replay, get the fill pokedex cheat, then u have full pokedex!
luck You CAN get shiny Pokemon WITHOUT a full Pokedex(I have done it :P)
You get the national dex by seeing every Pokemon in the Sinnoh dex. But don't worry you only have to see them in battle not catch them. When your dex is full go to profeser rowan in sandgem.
You can't. Not without and not with the national dex, ou can't get to other regions at all in Pokemon Diamond and Pearl
get an action replay, get Pokemon modifier and full pokedex cheats, then find arceas!
Go on Neoseeker. They have it.
my friend told me you have to get the national pokedex and then go to canalave dock and then ask for a ride. Then ask to go to (full\new) moon island. Then you can catch creselia!!
You need to get the official Pokemon full pokedex guide vol 2
If you mean cresselia, go to canalave city and ask the man by the boat to go to full moon island, if the option iosn't their have you completed Pokemon leageue and got the national pokedex from seeing 150 Pokemon in sinnoh
after you beat elite4 and champ you have to get full pokedex to go to stark mountain and tons of slugma and macargos
you only have to see every Pokemon that lives in the reigon. To find out where they all are, use this site. http://bulbapedia.bulbagarden.net/wiki/Main_Page