How do you catch Garintina on pearl?

You need the National Pokedex . You go to Route 214 then you go to Spring Path. Eventually you will come to Turnback Cave. It's hard to get to Giratina but, it's worth it! you dont have to use a master ball to catch giratina you need

10 dusk balls

2 ultra balls

and 6 timer balls

you need to lower his hp till its red and bring a staraftor(because hes almost unafected by anything)that knows defog so you dont hurt garintina when hes on red and use it over and over again till you think you had enough turns then use all your dusk balls then your ultra balls and finally use your timer balls till you catch him :)