Don't cheat.

"Thanks for the offer", you say. "But I feel that it's against the spirit of the Tournament to cheat."

Cedric shrugs.

"That's noble of you", he comments. "I'm sure that neither Fleur nor Krum have those qualms."

Feeling some sort of camaraderie between the two of you, you challenge Cedric to a friendly Quidditch match, just between the two of you. Cedric readily agrees, and you fly together for some time. After an hour, you start to flag. As such, you fail to see Cedric flying towards you. He hits you, and you both go tumbling head over heels in the air. You hit the ground with a sickening thud, and, before you black out, hear Cedric calling your name anxiously.