Which of the following bar practices should be avoided?

Dunking the faucet in beer while pouring should be avoided because it can introduce contamination into the beer. This practice risks transferring bacteria or residues from the tap into the beer, potentially affecting the flavor and quality of the drink. Additionally, any residue that might be on the faucet could taint the next pour, leading to an overall decrease in the beer's enjoyment and safety.

In contrast, air drying beer glassware is a good practice, as it helps minimize water spots and maintains the beer's head retention. Holding the faucet handle at the base while pouring is also advisable, as it reduces the risk of contamination from hands that might have touched other surfaces. Rinsing glasses with water before filling them is typically done to ensure that the glass is clean and removes any potential off-flavors from previous drinks. This pre-rinse can improve the beer's taste by ensuring the glass is not affecting the beer's characteristics.