Laying up for winter

Hi all

we have had our (1st) caravan now since May and thoroughly enjoyed our time away to date. We have now decided to 'lay it up' over the winter. It will be on our driveway with EHU available. It will also be fully covered with a protec cover but its design still allows access into the caravan. I am concerned about the possibility of dampness and am looking for some sound advice. A friend told me that when he first over wintered his van he switched the heating on for a couple of hours each week but this actually caused some real damp issues which he didn't discover until months later! I've also been told to leave saucers of salt in the caravan to soak up any air moisture or by a dehumidifier . What do those who know more than me do?