Be on the lookout
Sometimes students set the widest range possible, from 1 to 255. Later on, they are surprised when their robot triggers unexpectedly. (Basically what happens is that any message sent across the room triggers it. This can lead to some surprises when different groups in the same room are sending messages at the same time.)
What you can do: Tell students that it is important to limit the range and to coordinate it with the sender. Explain that the wider the range, the more incoming messages will be evaluated as true.
Here is an analogy that might be useful. Describe a situation where at school, each class has a letter code. When the letter is announced, itís their turn to go to the cafeteria. Ask students what would happen if a teacher instructed a class to go to the cafeteria when they hear any of the letters in the alphabet.
Sometimes students think that a robot can be either a sender or a receiver but not both. In fact, a robot can send and receive messages within the same program.