Park in spaces provided to avoid fines. You can park without any time limits/payment on the white lined bays. Blue lined parking bays mean that they are fee based and you should obtain a ticket from the parking meter.
The ‘disco orario’ sign means that you do not pay but you need to put a note with the time you arrived and there is a time-limit.
In Varenna you need to buy a parking ticket from the ‘Tabacchi’ shop, on which, you will need to scratch the year, date and time you arrived, the same is valid in most parts of Milano.
Parking is not expensive but it can be difficult to find spaces in the centre of towns and lakeside resorts in the high season.