One of the most important things is to avoid the pot becoming waterlogged. Not only could waterlogged soil kill the plant, but it could also result in the pot cracking. This happens because the water will expand when frozen, putting extra pressure on the sides of the pot.
If you haven’t already done so, lift the pots so that they aren’t resting on the ground.
Terracotta ‘feet’ can be bought from most garden centres. Alternatively, bricks or anything else with a solid, level surface can also be used.
As bricks are quite deep, they could be tricky to manoeuvre in place under a pot full of soil.
Raising pots off the ground can be done fairly easily with two people. One person pulls the pot backwards, raising one side, whilst the other person places the support under one side.
Then, repeat the process on the other side of the pot; ideally adding a third support to obtain the best form of stability. Lastly, do consider wrapping them with bubble wrap or horticultural fleece as an added form of protection.