I love autumn, and I treat it like a new school year for myself!
• Buy new stationery (a diary, pens, stamps for post, etc) and sort out my old ones. Go big or stock up at the supermarket/Poundland, where they do a surprising selection of planners and pen sets.
• Think about goals for the rest of the year - I think with the weather tending to be shit it's good to have something to achieve eg get rid or sell X amount of items each month, complete a series of workouts off YouTube or Nike.
• Learning: again, poor weather means being indoors more often, so take up a new class or attempt to seriously learn something on your own (using free apps, YouTube videos, online articles, books from library, podcasts). Plan out what you'll be using, when and for how long you'll learn each week, and set yourself a target end date. It could be a specific topic slightly related to your work, or a new language, or watercolours for beginners...
• Uniform, ie cull the closet and make dark mornings easier by creating a uniform for your work days.
• Breaktime: Prep your outdoor gear. Wellies/waterproof trainers, thermal layer, warm hat, decent socks, a coat... If you get outside each day for a brief walk then by the time the depths of Jan roll around it should be habit. If you find walks boring then give it a purpose, like 'I'll listen to 2 episodes of a podcast while I walk' or buying a newspaper.
• Packed lunch: Sort out your tupperwares and flasks. Write a list of basic dishes you can make that can go into a packed lunch for work or an outdoor picnic. Stock up on teabags, coffee, or hot squash mix (yuck).
• School trips: Look up the museums etc in your area, they'll either have already or will be soon releasing their AW program. Note down or book any events you'd like to see, invite a friend along so you have a social date to look forward to.
These aren't very practical preps, like winter proofing your house or anything, but lots of people have great lists for those online. :)