The Freeze Signal is used to communicate to students that they should suddenly stop what they are doing and pay attention to the teacher. I consider it an important safety measure. Personally, I use a singing bowl, but I have seen teachers use bells, wind chimes, and miniature xylophones. Use what works for you.
What is a Guided Discovery?
It is a student-centered approach to introducing materials and routines in the classroom, developed by the folks at Responsive Classroom. According to Lynn Bechtel and Paula Denton,
The primary goal of Guided Discovery is to generate interest and excitement about classroom resources and help children explore their possible uses. Guided Discovery also provides opportunities to introduce vocabulary, assess children’s prior knowledge, and teach responsible use and care of materials.
I would add that Guided Discoveries also build community. Students are asked to listen to each other, compliment one another, and really see and hear the work and ideas of their peers. Using this strategy I have built compassionate, organized, and respectful classrooms.