You cannot catch every single pokemon, unless you cheat. but, battle eveyone you see, even twice, and in this game you only have to see every pokemon, not own. So, go battle, walk in that grass, and you have it all by the end of the game.
By Trading.
Here is a list of all 150 Pokemon: http://www.serebii.net/diamondpearl/shinoudex.shtml The last Pokemon listed (#151) is not required to get the national pokedex.
you have to see all 150 Pokemon in the sinnoh poekdex
there are 150 kinds of Pokemon that you can see and/or obtain. Unless you have friend trade you Pokemon that you can only get in pearl to you, you'll never obtain them all. In Pokemon diamond and pearl all you have to do is see the Pokemon and you get its data unlike the older versions where you have to obtain them.
all sinnoh pokemon tips:just battle all wild pokemon.trainers,gymleaders,and elite4
There are only 150 of them
Pokemon 150 is Palkia, the Space Pokemon. You can find it at Spear Pillar.
Talk to the Proffessor; he'll give you a National Dex.
yes when you get the national dex
150
Get the National Pokedex from the proffesser when you have seen 150 Pokemon
hi,There are 150 Pokemon in the Sinnoh dex.Shadowfritsch