first you have to battle all the elite four after that you can catch it..............but i don't now where to catch giratina
go to tunbat caveand walk through the rooms
check in the pokedex
How to catch giratina in Pokemon white? For me i got it by transfering it in the Pokemon transferer maybe you can do that.
no
you find it at giratina lake
in map 6
defeat all gyms,elite 4 and champion of that region to catch legendary pokemon
Giratina
Yes, you do have to save them in order to catch Giratina.
a utra ball or a master ball
map 9 and 2 1 water Pokemon
its been confirmed you can catch it in Pokemon platinum pearl and diamond