you can find it in pastoria city
at route 230 while you are surfing
in or on top of mt coronet
In the wild or from professor oak
You can't find Bulbasaur in the wild on Pokemon Diamond or Pearl (not sure about Platinum).
You can find them wild by Pal Park, down and to the left of sandgem, or catch a bonsly as a special Pokemon in the trophy garden
you can't find a gardevior in the wild
Mantine is not available in the wild in Platinum.
In the woods.
you can find a wild kirlia in the Pokemon mansion area but not in the Pokemon mansion
in mt cornet
You can find wild Sudowoodo at Route 221.
A Buizel can be found in the wild grass at Valley Windworks.
You cant find a "Wild" Milotic. You must find a wild Feebas and give it max beauty then train it one level.
It's impossible to find in the wild. You need to evolve Haunter.
U can sometimes find them on wild poliwhirl
at route 230 while you are surfing
in or on top of mt coronet