Take pictures. I know, you are thinking, that's it? That's your big tip? Hear me out on this one.
Many teachers take photos of their classroom, but these pictures are pictures with a purpose. Think of them as maps that will guide you year after year.
When you hang up your posters, design that gorgeous bulletin board, or set up your supplies just so, take pictures.
Save the pictures on your phone or computer or print them out and keep them with your decorations.
Note: I took my pictures at the end of the year (you can see my storage boxes and mess), but I would do it at the beginning of the year so you don't forget. You can always take more pictures later.
If you change your bulletin board with the seasons or create special displays in the hallway as the year goes on, don't forget to take pictures of those too.
Then when next year rolls around, you don't have to waste time figuring out how to layout your posters on the wall so they all fit or try to remember how you hung those lights over your desk.
With your photo "maps" from the previous year, you will finish decorating your room quickly and can then use your time for planning those awesome first day lessons. You can even have your spouse or child or friend or colleague help you because they can just look at your photo "maps" rather than needing so much of your guidance that their help is no longer helpful.