This is so exciting!
So make sure camera battery is loaded!!
Have ID tag made up (it's a legal requirement anyway) and decide on a comfortable secure collar, with a nice length lead (NOT an extending one). Plenty of poo bags!
Start thinking about insurance and make this your top priority as soon as dog comes home with you. Also don't forget to update microchip details as quickly as possible.
I'd recommend stainless steel for water and feed bowls - easy to keep clean and non breakable.
Grooming - although rotties have short coats, they will still need regular brushing so a nice grooming mitt will be great - you will also find they enjoy being groomed and it is a very convivial way of bonding with dog. Ours love it. Once home from kennels, they often have that "kennel" smell and you will probably want to give them a bath - again a variety of doggy shampoos around - take a look in PAH or your local pet shop.
Think about car/transport - how/where will dog travel? In boot? In back seat? In cage? Think about safe, secure transportation. A heavy dog unsecured on back seat is lethal and could kill you and themselves in an accident. Also useful to keep in car, wet wipes, towels, water for after walks, a few treats, spare collar and lead, plus doggy first aid kit.
Identify and prepare to register with local vets. Once chosen make sure vet's number is in both your mobile phones (along with Council dog warden for emergencies). Mark on calendar dates for annual vax, and regular treatments for worming/fleas/ticks etc.
Identify and prepare to register with local training classes ( a fantastic way to bond with the new arrival and also great fun, and v social).
In house, will dog be in all areas or are you gating off any areas? Make sure garden is fully secure.
Beds - very much a matter of personal preference (both for you and the dog). You can go for anything from a top of the range Orvis one or the budget approach of a folded Ikea duvet and cover. If any sort of fabric, it must be washable (and washing regularly at high temps will also help to break flea egg cycles too, as well as reducing smells).
Food.
Training treats. Clicker. Kong and any toys.
Good luck! 