Pre-warm your pots, pans and trays. This tip came all the way from Oslo, Norway courtesy of Jannike - many thanks! Store your trays and dishes in the simmering and warming ovens (if you have them) the night before and pile pots and pans you may need on a drying rack on the hob (pre-warming cats is not necessary!). It saves the energy your cooker would normally use to warm these pans on Christmas day. Genius!