I mash the fruit (rough chop of large fruit, try to pierce each berry for something small like currants or blueberries), put it in a bag, put the bag in the must and add pectinase, give it 24 hours for the pectinase to do its thing and then check the SG and add the yeast. If it's a fruit that's likely to spoil before I get the yeast in there, I'll sometimes steam it first or use 1 campden tablet per gallon 24 hours before I add the pectinase. So far the only fruit I find I have to do this with regularly is pears, I don't bother steaming, boiling or sulphiting any other fruits unless my batch is less than optimum and I've got apples that are starting to ferment on their own or fruit that's been baldy bruised through rough handling.