Numbers: As for last week's party, allow half a bottle for each person and a bit extra for luck, with roughly one third of the total white and two-thirds red unless there is some reason (fish? tannin allergy?) why the proportions should swing the other way.
Colours: At an informal buffet party, it's fine for the host to grasp a bottle of each colour and go around asking "Are you on white or red?" But this time you're out to impress - remember? - so do it by the book. Pour white with the first course, red with the main (unless the menu dictates otherwise). Civilised guests are supposed to enjoy both. Temperature control: Whites not too cold, reds not too hot. To do good wines justice, limit time in the fridge or anywhere near that roaring fire.