Kitchen appliances should be disconnected either a day or two prior to moving day, or in the morning before you start moving items.
Always turn off the power 1st, then disconnect the appliance as required.
Washing machines and dishwashers will need the water supply turned off before unscrewing water pipes and waste pipes. It's worth giving the pipes a good shake before you move them, as water quiet often gets stuck in the pipes, and can drip out while being transported on the van. If you still have your transit bolts from the washing machine you can re-insert them for transit.
Freezers should be defrosted a day or two prior to the move, and once in your new property, give them a couple of hours to settle before switching back on the power, to avoid any little accidents with the refrigeration gases.
If your appliances are not as simple as unplugging and moving, like some gas and electric cookers, make sure you get a professional in to disconnect them for you.