Understand your preferred teaching style. Some instructors prefer to choose textbooks that diverge slightly from their point of view; others prefer textbooks that survey the course subject and provide dry facts. Knowing your teaching style is critical when reviewing textbooks; without knowing it, you may review more textbooks than needed.
Reach out to several of the main textbook publishers and review their offerings for your course subject.
Review and make a list of pros and cons for each book. When reading, consider the following: the structure of the book and how it relates to the structure of your course, the material presented and how understandable it would be to a student, how appropriate the textbook is for your audience and its readability.
Price the three highest-ranked textbooks. If the second-highest-ranked book is substantially cheaper than the first, and there is not a major difference in the quality of the textbook, your students might appreciate the cheaper of the two.