1. Look at the patrons physical characteristics such as the speed which they walk or speak. Consider their size and gender in proportion to how much they drank. Women have a lower tolerance than men.
2. Be on the look-out for the customer’s inhibitions to become lowered. They will usually display signs of louder talking, more sociable and talkative, outgoing beyond what is normal for them
3. Often intoxicated patrons will behave in a way that is unlike their normal behaviour such as using bad language, being louder than usual, becoming overly flirtatious and displaying generally poor judgement.
4. You could also observe their physical appearance because their eyes may become red and bloodshot, their speech slurred or may even display signs of being forgetful. Talking slowly or moving slowly is also a sign.
5. A common sign is showing lack of coordination that causes stumbling, swaying, falling down, dropping glasses etc.
6. The person may stink of alcohol and be sweating more than normal.

By watching out for early signs, bartenders, waitrons and other alcohol service staff can prevent customers getting to the stage of over intoxication which is usually when it becomes a problem.