When your son or daughter wants to throw an informal party for their friends, you will probably find yourself deeply involved. They may well still live with you (so their home is your home), or - even if they are away at university etc. - may still regard the family home as their personal property.
In an ideal world, you should organise the party in another venue (hotel, bar, club etc.), but in reality this is an expensive option, which not everyone can afford. If you do feel obliged to offer your home, take some simple precautions:
•If at all possible, make the garden the focus of activities (bad news for those with winter birthdays).
•Remove all valuable or breakable items, roll back carpets, or cover them with old rugs or carpet offcuts. Drape light-coloured upholstery with throws (or even sheets).
•Keep certain rooms (e.g. your bedroom or study) off-limits. Put a No Entry sign on the door, and lock it if at all possible. If you can't lock the door, drag a heavy item of furniture in front of it -- it will at least act as a disincentive.
•Supply the drink, or at least supervise the purchasing of it. Stick to wine and beer - no spirits, and no lethal fruit punches (often they taste innocuous but are extremely strong, with predictable results…).
•Provide plenty of stodgy food - bread, rice and pasta salads, or baked potatoes are all ideal ways of soaking up the alcohol.
•Impose a curfew - i.e. an agreed time when the music stops and the guests depart. Then warn the neighbours…
•If you've got the nerve, go out for at least part of the evening; no self-respecting party host is going to appreciate the spectre of their anxious parents in the background. But don't stray far from home; you'll need to be on hand if there's an emergency or a dispute with neighbours.