search for Pokemon in every grass patch you see, look for trainers, surf, use rock smash, just do everything you can to find them. be patient. the results rock.
You have see to many different pokemons. Then you will fill it (you have to every Pokemon to get national pokedex).
use action replay
Yes you can. You just have to fill up your pokedex and talk to pr.Rowan.
beat every trainer do not skip
you just have to play the game
you fill up the sino pokedex
fill your pokedex and battle more trainers
Fill up your Sinnoh pokedex. Here's something that will help you: Rotom.
try transferring Pokemon back and forth from diamond, pearl, or platinum. that way, the pokedex in both games are filled.
no they don't add Pokemon into your pokedex there
you have to win the champion and fill your pokedex. (^^)
To get the Poke Radar you gotta fill up the Sinnoh Pokedex, talk to the professor, and he will give you the National Pokedex and the Poke Radar.