Inviting a baby into your home can be a fraught affair. Your expectations of how a baby should behave may not be the same as the parents', and tensions and difficulties can ensue.
Prepare for a baby visitor. Remove breakables so that they are beyond a baby's reach, secure kitchen cupboards if possible, move a piece of furniture in front of the bottom of the stairs. At least you have now done the bare minimum to safeguard the child's safety.
GUidelines for hosting baby visitors
If you are hosting new parents (even if it's just for a few hours) make sure that they have the sole use of a room in your house. They'll be able to dump their baby paraphernalia, retire here to change nappies, breastfeed, or just have quiet time with the baby. They may be able to set up a carry cot in this room and put the baby down for a nap. You'll benefit from allocating them their own space, as otherwise they'll inevitably colonise your whole house (it's difficult to avoid), and you may feel invaded.
Test your own tolerance. If a baby creates a certain amounts of mess (saucepans on floor, books taken off shelves, newspapers shredded around sitting room), can you live with it? If all that it entails is a quick 5-minute tidy around once the baby's gone home, then you almost certainly can. Why make a fuss over something that is comparatively trivial?
Communicate with the parents. If a baby is doing something that you can't bear to witness (playing with your best china, breaking the flowers off your precious pot plants, smearing jam on your white upholstery), point it out - quietly and firmly - to the parents.
Never react directly to the baby - snatching it away, shouting etc. will cause open-mouthed shock followed, inevitably, by lusty screaming and pained looks of reproach from the parents.