Use only vegetable oil like the "Canola" brand to maintain the shine that the boards have when you first purchase.
DO NOT put the boards through the dishwasher, this will crack, fade and ruin your board.
When you first get your board home, rub oil over the surface, ends and sides and you will see how some areas soak up more than others. The heartwood areas will soak, the sap wood on the outer layers of the tree will not. Your board is made up of random laminates of these woods.
Remember your board may have spent 800 years growing and 60 years in a building.
Warning: oiling can be therapeutic.