One possible exercise:

Have an instructor ask the students to direct the instructor in a certain task (tie a shoe, open a wine bottle, anything). Instructor does what the students say in a very literal manner, perhaps intentionally misunderstanding vague terms.

The idea, of course, that the students will get told, by instructors or each other, again and again to be specific, but they'll get rapid feedback about what works and what doesn't.

This is adaptable to other scenarios: Students in pairs write directions for each other for some task, swap papers and then get to play the intentionally obtuse role (which can be fun). This brings out a competitive aspect, where students can win by being the most clear.