Mum want's me to put up curtain rails (the old ones are gone and the wall has been replastered after the insertion of new windows). Is it as simple as drilling holes in the right place, and screwing the rail holder into position? I want to know how to pick the right drill bit (just a bit smaller than the screw? do packs of screws give a diameter or does it have a special jargon name?) and what might go wrong (walls crumbling)?