If you can, try to imagine how it will be for the child. They will be feeling very apprehensive too.
Be gentle and have some nice activities lined up at home and out and about that are age are appropriate and that don't cost loads so it doesn't matter if you don't do them.
Don't buy loads of stuff because you don't know what they will arrive with. If they need stuff you can choose it together. However, do make sure that you have double sets of mattress protectors and bedding in case you have a wet bed first night, you'll need to have dry bedding ready to switch quickly and without fuss.
Make sure the SW tells you any routines they have, bedtime, food, school etc. Try to stick to them if you can.
Have a little welcome book with pictures and your house rules so these things are talked about as part of your welcome. Things like what to do if they need more loo roll, what to wear around the house.
Make the room welcoming with something soft and comforting available, but don't be disappointed if they bring their own comforters and reject yours.
Have some strategies for dealing with behaviour and settling difficulties. Be prepared to have a lot of unsettled nights at first, but equally be prepared for a change to unsettled after a few weeks- attachment stuff doesn't always show at the start.
Smile, open your heart and prepare to be challenged and to fall in love.