So, neither the game guide or the internet were much help in defeating Cerberus. They offered different strategies to be sure, but I still wasn't beating him using physical attacks like they suggested. I decided to try one last strategy before I gave up and begged one of my cousins for help (I'm impatient, so sue me). Whoever posted that getting on Cerberus' back and hitting him in the head with the keyblade obviously didn't try it, because you can't - or I couldn't anyway - without falling off his back while never actually hitting him. BUT, staying on his back made it super-easy to cast magic without worrying about Sora-Seeking Magic-Vomit! A quick trip back to Traverse Town for Ethers, a rearranging of equipment and voila. K.O.'d Cerberus. Next level please!