Always choose a dry day for making any confections that call for cooked sugar. Excessive humidity in the air will be absorbed by the sugar after it is cooked, causing it to become soft and sticky.
For safety, always have a bowl of ice water (mostly ice) at hand when cooking sugar. In case of burns, a quick immersion in the cold water will stop the effects of the hot sugar, which has a tendency to stick to the skin.
When a pan of cooked sugar comes off the heat, rest it for a moment in the same bowl of ice water. This will prevent the heat retained by the pan from continuing to cook the sugar beyond the degree necessary for the recipe.
Washing the inside of the pan with a clean brush dipped in cold water is the most important part of cooking a sugar syrup. Doing so keeps stray sugar crystals from sticking to the pan and crystallizing the entire batch of syrup during cooking.
If a batch of syrup does crystallize, add 2 tablespoons water and lower the heat to the minimum, stirring occasionally until the syrup returns to a boil. Wash the inside of the pan with a clean brush dipped in cold water before and after the syrup returns to a boil.