Always be clean, tidy and diplomatic.
Always rinse/wash bar equipment like cocktail shakers and strainers after use, even between drinks.
Always wash and dry your hands frequently, especially after contact with citrus fruit/juices. This helps prevent hand dermititis.
Look after your hands, especially your fingernails, as these are always in view. Keep fingernails short, and if using nail polish, use neutral colours.
Don't smoke or drink while working behind a bar, it is considered unsanitary and in many countries is also illegal.
Don't allow a champagne corks to 'pop' on removal, this is of bad taste and dangerous.
Handle a glass soda siphon by the plastic or metal part only. The heat of your hand may cause the glass to shatter.
Never fill a glass to the brim.