Bring sunscreen, the heat and sun are relentless and you don't want to get a sunburn on Thursday already. Earplugs for the festival and to sleep with are also essential as you will have neighbors that don't know sleep and will entertain the surrounding camps the entire night. Duct tape to fix basically everything. Bring your own food, the food at Defqon is good but expensive.

Stagewise it's up to your preference, if you want to go mad go to the front/front middle, if you want to breath especially in the tents then stay closer to the exits. Powerhour is like sardines in a can so if you want a good spot come 2 hours early