Vet appointment for vaccinations. Parvo is out there - I know of a puppy who recently died from it.
Also sort out flea and work treatment with the vet. Ours does a scheme where you pay so much a month and get all the flea and work stuff, plus a reduction on all consultations, operations, etc.
An identity tag for when the puppy can go out. We use brass slide tags from Identitag. They cost about a fiver, arrive very quickly, and can be used with a buckle (not a clip) collar. They don't get lost, unlike dangling tags.
Is the puppy coming with a starter pack of food? If not, lay in some.of whatever the breeder is feeding, and give your puppy a few days before you switch to anything else (if you do).
Depending on how active you and your new dog are likely to be, it might wise to set up a basic first aid kit - saline to flush a wound or an eye, wound powder to disinfect and slow bleeding, low adhesion dressing, conforming bandage, vet wrap, tweezers, tick remover, scissors, Piriton. We have this and more and it's saved us a fortune over the years.
Acquire some indifference to the state of your garden.
Oh, and patience. Lay in massive stores of patience, because puppies are lovely but also pains in the arse!