Which of the following is a practice to avoid when preventing channeling?

The practice to avoid when preventing channeling is to be cautious while tapping the portafilter side. Tapping the portafilter gently after tamping can help settle the coffee grounds into a uniform layer; however, being overly cautious can lead to insufficient settling or an uneven distribution of coffee grounds. When the coffee grounds are not evenly distributed or compacted properly, it increases the risk of channeling, where water creates pathways through the coffee puck instead of extracting evenly.

In contrast, evenly distributing grounds during grinding, tamping with bodyweight, and rotating evenly during grinding are all techniques aimed at ensuring a uniform coffee bed. Proper distribution and consistency in tamping pressure are crucial for achieving an even extraction during brewing, thereby reducing the chances of channeling.