If you have a compost heap, add some leaves in with everything else, although don’t fill the heap with leaves. As with most compost heaps, aim for a good mixture.
For surplus leaves, or if you are short of space, you can collect and store the leaves in bin bags. When the bag is full sprinkle the leaves with a little water,tie a knot in the top of the bags and puncture with some holes to let in air. Otherwise the leaves will just go slimy. Store in the shade and leaves will rot down to a crumbly mixture that can be used as a mulch the following autumn.
Although it may look a little untidy you could alternatively just let the leaves stay where they are in borders and under hedging and they will naturally rot down on their own.