Prepare for a cold winter

I have spent the last few months creating a garden around my new house. Therefore this is the first winter I am facing as a gardener. With some forecasts predicting another extremely cold winter what can I do now to prepare my garden for another event like last December January? I have a mix of everything throughout the garden. Young Trees, evergreen shrubs, laurel, roses, hebe, cordelli, grasses, perennials, lavander, heather etc etc. Any advice is greatly appreciated.