After you complete the national Pokedex, just like in other games, just wander around, doing stuff like maybe training Pokemon to level 100, entering the lottery, entering contests or, if you have not caught them all yet, catch some legendary Pokemon.
What you have to do is catch all the Pokemon from all the other regions(complete national dex.
Complete the sinnoh dex
No is doesn't only if you complete the national dex
Complete National Dex, it takes forever
you have to complete the sinnoh dex then go to the pal park,in the grass!
No, there is not a Pokedex after the National Pokedex in Pokemon Diamond Version.
yes and to do so just see all the Pokemon in sinnoh to complete the sinnoh dex
=you first have to complete the sinnoh dex,this is not that hard.==however the national dex is,YOU HAVE TO CATCH EVERY POKEMON THERE IS!!!!!!!!!!!!!!== you HAVE to trade and migrate,==hope it helped!==^_^=
you compete the sinnoh dex.
You have to complete the Sinnoh Poke`dex if you have platinum, diamond, or pearl. Then talk to Prof. Rowan.
Complete your Sinnoh Pokedex and talk to Professor Rowan. You get the National Dex and a Poke Radar.
Just train your Pokemon till they are all level 100 then battle your friends.