half a glass should do it. depends on the length and type of party you are hosting too though...

some people drinking over the course of 2-3 hours can drink up to a full bottle, while others may only have 1 glass.

on average 1/2 bottle per head should suffice.
depending on how well you know your crowd, you can adjust as necessary.

can't hurt to buy another bottle or two to keep as an emergency reserve either, incase the party is still going strong and your reserve is running low... :)

if you don't use it for the party, it can't hurt to have an extra bottle or two laying around. i'm sure it will be enjoyed eventually!

my new favorite way to serve wine:
http://www.anthropologie.com/anthro/catalog/productdetail.jsp?pushId=HOME-ROOM-SCIENCE&id=973411&sortProperties=&navCount=0&parentid=THERES_ALSO&color=100&isProduct=&fromCategoryPage=&navAction=leaf&isSubcategory=&popId=HOME-ROOM

Seriously? a "wine tumbler"? Why not just use a red plastic cup?

and the ceramic wine decanter... It's a BOWL! Sure, it'll aerate your wine, but how are you going to pour it into a glass from there?

jumpyfroggy -I believe the tags on the first and third photos are switched; the "bowl" is glazed - it's a coaster to put the bottle in so as not to drip on the table. The first photo, the strange hollow pitcher thing, is the decanter.

Red plastic cups!? The post is about "dressing up your wine." How did you not get that jumpyfroggy?

Mixing and Matching tumblers is a great way to add a little flair to any beverage.

I was also concerned about the bowl-shaped aerator, thanks neerland!

I really like drinking out of non-wine glasses. I think it can make things festive without feeling stuffy. I rarely use a wine glass for my casual situations.