They want to see your house as it normally is. Of course pick up a bit before the visit as you would if a friend were coming over. The purpose of the visit is to see where the foster child will sleep and to know that the house is safe. Definitely do NOT buy new stuff or move the things you mentioned out of site. the boxes are OK as long as they're not next to the furnace which would be a possible fire hazard. They are a part of everyday living and are perfectly acceptable.
I was a foster parent and have taken children to foster homes. Please try to relax. This visit is just routine and only done to know more about the home in which a foster child will reside. Safety is the main issue. A side issue is how comfortable you are in your own home. They definitely expect your home to look lived in.
BTW at this point you do not need to have done all the child proofing mentioned by Bug. They will tell you at this visit what needs to be done. Unless you're fostering toddlers much of what she mentioned doesn't ever have to be in place. I suggest that the home she's describing happened after the first visit and even then her friend may have decided on her own to do some of these things.
If you try to hard to make sure your home meets all possible safety standards you won't know if you're over reacting or not. Of course, maintain the common sense strategies that you already have in place.
If you go out and buy and install and lock up all the things that Bug suggests you won't know what is actually required by CSD. Look at this visit as a way to learn what is required in addition to what you already have. Some examples. I never did take a child to a home with a fenced back yard, a lock on the basement door or even locks on all cabinet doors and drawers, tho locking up medicines is a good idea for any home. I had cleaning supplies under the kitchen sink and in the lower cabinets without locks. My shredder was on the floor.But then I was certified for school age children.