I suppose it depends where you want to go, but for a first trip I would recommend you go to the Interlaken area. There are many sites you can book through the Caravan Club, and others, but we have always used Manor Farm. It is right on the lake, with good facilities and a very good restaurant. Switzerland is NOT cheap, especially eating out, but try the Coop in Interlaken for better value,they weigh your plate to charge you!!!!
Read up about travel cards for using on the trains, cable cars and steamers. These can give you very good value.
A good entry point for this area would be at Basle using the German motorway through Basle itself. Don't forget you will have to pay 80 Swiss Francs ( about