try rare candies
level him up to level 35
I can't level up your rayquaza but I can level up mine.
Elite 4
YOU LEVEL IT UP PATIENTLY!!!!!!!!!!!!!!
no point hacking u no...
Get a corphish and level it up to level 20 or so and it will become crawdaunt.
You catch a Slakoth in Petalburg Woods then level it up to level 18.
cheat
Repeatedly battle the Elite 4 with high level Pokemon with the Pokemon you want to level up holding an exp. share.
To up your Pokemon's to 100lv you have to fight the elite 4 100 time ......
use a weak poekemon in battle
catch an Abra and use your gameshark for rare candeys and then level it up! :)