BarBug Straight Up: The choice of whether a drink is served on the rocks , neat (or straight up) is a personal taste issue. You can always experiment.
Keep lots of ice around when entertaining - it goes fast when mixing and shaking drinks. It is always recommended that you use clean pure water for ice. Some freezers can cause food odor to become buried into the ice and this can ruin a good drink. ice purchased at your local market is usually clean and odor free, otherwise they wouldn't get much repeat business.
If a recipe indicates a "chilled" glass, you can keep the glass in the freezer or refrigerator for a while or put ice in it while mixing the ingredients in your mixing glass. To minimize the wasting of ice during a party or other social function, you can also place glasses in a bowl of ice to chill them. A chilled glass helps keep the drink cool longer.
The following glass sizes are commonly available and are those suggested in Barbug recipes. At a minimum you should have a few each of the 4 oz cocktail glasses, 12 oz collins glasses, 8 oz highball glasses, 6 oz rocks glasses, 2 oz cordials and some all purpose 10 oz wine glasses.