What should be considered when elementary school students are introduced to new number ranges? How can they be supported in problem-solving? How can second graders actually learn to calculate instead of just counting? These are just three of the questions that mathematics teachers in elementary schools often ask themselves. This practical guide offers suggestions, support, and exemplary solutions. It is a comprehensive resource for mathematics instruction in elementary schools! The volume outlines the goals, content, and didactic guiding principles of contemporary mathematics teaching in a compact and illustrative manner. In addition to fundamental background information for professional lesson preparation and execution, it includes ten example topics with concrete, practice-tested teaching suggestions, as well as references to further materials for teaching and self-education. This practical guide is primarily aimed at teachers who are not specialized in mathematics and those in teacher training. However, it also provides experienced educators with new ideas and fresh impulses for their teaching practice.