One glass per person is sufficient, especially if people will be standing up or walking around. Make sure to provide opaque pitchers to pour excess wine into, so that people don’t have to drink everything in their glasses. Choose good, all-purpose glasses—the Riedel Vinum Zinfandel is ideal for tasting both red and white wines.
Six to 10 wines is a good range for a tasting; any more, and people tend to lose track of which ones they’ve tried. A tasting pour is about two ounces, which means there are 12 tasting pours per bottle.
Making a tasting sheet listing each wine, with space for comments, is a nice touch; it’s also helpful to have background information on each wine—the price, where to buy it, who made it, interesting facts about the vineyard or grape variety and so on.