Time to harvest all those fallen leaves, just avoid walnut, laurel, holly and other leathery leaves. I have used mainly horse chestnut, sycamore and lime though oak, hornbeam and beech are usually recommended. I use a mower to mince them up a bit, if you want them really fine, do it twice. I stick at once and that takes long enough. Traditionally they are put in an enclosure that allows good airflow but I use two 'daleks', they are not much use for actual compost. I alternate layers of leaves then a thick layer of coffee grounds. if the leaves are dry I thoroughly wet each layer of leaves after putting it in. I leave the lids off the daleks but either leave them a little short of full so the wind doesn't blow them away or put a heavy wire mat over them. I have used a builders bulk bag in the past to hold them. Fill it then pierce the sides with a pickaxe if you feel the need, I didn't bother. If you are given, or acquire bags that are too ripped to use, all is not lost, cut them up for strawberry mats! I leave the leaves for two years but gather them every year so that each year I have a supply of crumbly leafmould.