Autumn is a critical period in your lawn care regime. A little work now can reap big rewards in the Spring time.
Keep your lawn tidy. As leaves fall remove them regularly so they don't damage the lawn by blocking out light and trapping in moisture. Don't waste the leaves but make leaf mould from them, an excellent soil improver.
As the weather cools down and the grass growth slows raise the setting of your mower to a higher cutting height to avoid damaging the lawn.
It is a great time to apply moss remover before the ground cools. Again it will make a big difference come the Spring time.
Feed and condition with an Autumn grass feed. The different formula of Autumn feeds will toughen up the grass and strengthen the roots to help it survive the harsh winter conditions.