You can avoid lots of plant losses by following David’s advice. Take to heart the few advantages of mediterranean gardening – no digging over of beds, no lugging of manure.
Right now this month look at all the plants already growing on your plot and give them a good pruning. If they’re wild plants and a bit big and unruly, one option is to raise them off the ground by pruning all side branches from the lower trunks/stems. Now you have a little shade for your newbies.
Next haunt the nurseries for young plants – they’ll settle in quicker because their roots won’t be twirling so much in the pot.
Wait for some autumn rain. Dig some big holes with a pickaxe and fill to the top with water once or twice. Mix a little of whatever good soil you can find (homemade compost, spent potting compost, old manure etc.) with the soil from the hole – there won’t be enough otherwise because half the hole will probably have been stones. Make a mound of soil in the bottom of the hole and arrange the roots you’ve teased from the root ball over it. Backfill leaving a decent watering hollow and keep an eye on the plant for the rest of the winter. Water regularly during the drought season for at least two summers. Despite what Olivier Filippi recommends I find that here in Attica I can rarely give up watering all together despite regular mulching.
Good luck is also a necessity.