A few words from The Savoy Cocktail Book

A Few Hints for the Young Mixer (from The Savoy Cocktail Book)

1. Ice is nearly always an absolute essential for any Cocktail.
2. Never use the same ice twice.
3. Remember that the ingredients mix better in a shaker rather larger than is necessary to contain them.
4. Shake the shaker as hard as you can: don't just rock it: you are trying to wake it up, not send it to sleep!
5. If possible, ice your glasses before using them.
6. Drink your Cocktail as soon as possible. Harry Craddock was once asked what was the best way to drink a Cocktail: "Quickly," replied that great man, "while it's laughing at you!"

A few additional words from me:

Many people seem to underestimate the importance of ice. As quoted above, ice is clearly one of the most important features of a cocktail. A lack of ice is a real detriment to a party; make sure you stock up! Get a bunch of ice, a couple of ice buckets, some booze, and you're good to go. Even straight alcohol benefits from some ice, so use it liberally.