What is one of the best ways that seller-servers can be sure?

that they are not serving alcohol to minors.

One of the best ways that seller-servers can be sure that they are not serving alcohol to minors is by verifying the age of the customers, particularly the ones who appear youthful. There are various methods that businesses can use to do this, including checking the ID cards and driver's licenses of the customers to confirm their age.

For instance, some places may only accept government-issued identification, such as a valid passport, driver's license, or military ID. This approach can help to ensure that only those who have reached the legal drinking age can purchase alcoholic beverages. Another alternative is to rely on the state's ID scanning systems, which can accurately scan and verify IDs electronically.

Moreover, sellers could request a valid ID even when they don't suspect that the patron looks underage, as this can discourage people from trying to purchase alcohol from the establishment. It's also crucial that server-sellers are familiar with the local, state and federal regulations in place that govern the service of alcohol. They should be aware of the laws regarding identification, sales, and the consequences for violating such, including fines and the revocation of alcohol sales licenses.