i don't know the complete pokedex, so you basically start in twinleaf town and make a journey around the region and catch, battle, and work with Pokemon. when you have seen all the Pokemon the region has to offer, you go to prof. rowan and talk to him. then prof. oak comes and upgrades your pokedex to national mode. that is all i know.
There is only one legitimate way to complete the Sinnoh Pokedex. To complete the Sinnoh Pokedex you must trade for the missing Pokemon with Pokemon Diamond, Pearl or Platinum.
you have to complete the sinnoh pokedex and get the national pokedex hope i helped :P
complete the sinnoh pokedex
You have to complete the Sinnoh pokedex before haveing the national pokedex.
You get a ticket to sinnoh and and pokedex entries are expanded
You have to travel around Sinnoh to complete the Pokedex.
yes, but it is not needed to complete the pokedex
After you go to the Pokemon lab for the first time, Professer Rowan will ask if you would complete the Sinnoh pokedex. Answer "Yes". He will give you the Sinnoh pokedex. If I didn't answer your question right, try Psypoke.com If you don't have Pokemon Pearl/Diamond/Platinum you can't get the Sinnoh pokedex.
Please see the related link for a complete Pokedex from the Sinnoh region.
complete the sinnoh pokedex
First complete the sinnoh pokedex, 210 Pokemon
Just go to Pokemon platinum central and click on pokedex and it shows you where to battle all the Pokemon in sinnoh.