Facilitating mathematical investigations with teachers will help improve their teaching! Because a student's learning depends so heavily on teacher quality, districts and state departments of education, colleges, and universities are called upon to strengthen their teacher preparation and professional development programs. Yet college mathematics courses are often criticized for being disconnected from the mathematics that teachers are asked to teach. The Facilitator's Guide for Ways to Think About Mathematics is designed to close this gap. National and state standards and frameworks suggest that mathematical investigation, problem solving, and exploratory learning should play a central role in mathematics lessons. It is therefore necessary for teachers to experience mathematical explorations as learners themselves, which places new demands on professional development facilitators and preservice educators. This guide provides resources for facilitators to use while they are planning and implementing courses and workshops using Ways to Think About Mathematics. This guide and the accompanying CD-ROM contain: -Commentary on the activities -Pedagogical suggestions (materials sequencing, promoting active participation, adapting to the needs of particular teachers) -Various solution strategies -Additional reading and problems tied to the content of the main text -Sample solutions for all problems and discussion questions Ways to Think About Mathematics and the Facilitator's Guide will provide staff developers, preservice educators, and math department chairs with all the necessary tools to provide high-quality staff development in secondary mathematics. The materials were funded by the National Science Foundation and successfully field-tested in a wide variety of professional development and preservice settings.