They can't talk, but they can express emotions.
You can't talk to your Pokemon in Pokemon Platinum. Only in Pokemon Heartgold and Soulsilver.
go to the gym and talk to the guy
You walk up to him and press A.
talk to the man on the platform in pewter city
You get the pokegear from your mom after you talk to prof elm.
talk to your first party Pokemon behind you.
you have to beat team rocket and talk to the man in the dojo
Get to the end of it and talk to the Chinese woman.
talk to the guy in the pink suit and he gives you headbutt
on route 32 in the Pokemon centre talk to the fisherman
you go talk to prof. Oak
Talk to Blue on Cinnabar Island.