You can certainly use whatever you have on hand, but be sure to use a tall glass for those drinks calling for a collins glass so the drink will fit. 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.
BRANDY SNIFTER
Usually 3, 6, 10 or 12 oz. The 6 oz size is most common. Can be used as substitute for the drinks that call for a shot glass. CHAMPAGNE
4 to 6 oz stemmed specialty glass. COCKTAIL
Very versatile stemmed glass used for "straight up" drinks like the cream drinks and martinis. Sizes range from 3 to 6 oz but the 4 oz is the most common size. The larger 6 ounce saucer style is used for margaritas and frozen drinks. The 4 oz "V" shaped ones are commonly used for martinis. COFFEE
The common 8 to 12 oz coffee mugs. COLLINS
Tall and slender holding 10 to 14 oz, used for the drinks with the greatest liquid volumes. Sometimes frosted. CORDIAL
About 1 to 2 oz for some shot type drinks, liqueurs and layered delights. HIGHBALL
Similar shape to the collins glass but shorter and fatter of 8 to 12 oz. LARGE WINE
A stemmed round bowled 9 to 14 oz glass for red wine. MARGARITA
See COCKTAIL glass. OLD FASHIONED
The larger ROCKS type glass, 8 to 9 oz. ROCKS
The short, wide "on the rocks" glass holding 6 to 9 oz. SHOT
The common shot glass (or jigger) holds 1 1/2 oz. An actual "shot"glass may vary from 1 to 2 oz. A "pony shot" glass is 1 oz. (Buy one from Haxtons!) SOUR
A special 5 to 6 oz "cocktail" glass that has a taller and thinner bowl than the standard one. WINE
The standard 6 to 8 oz "white wine" style glass that is taller and thinner than the larger "red wine" glass. From Barbug