What should I take for a 12 hours plane travel?

Depends. It depends on what your problem might be. If you are not scared of flying, you may not take anything. Food and drinks will be provided while on board. If you can sleep well w/out using any supports (neck, back, etc.), then you are ready to fly. If you are traveling in business or first class, you will have plenty of amenities available to you for an enjoyable travel.