Students in introductory science laboratory courses benefit from comprehensive technical writing instruction. Written communication is an important skill for people in the workforce as well as education; STEM (science, technology, engineering, and mathematics) students need to develop good technical writing skills, and most enter college with little experience in this type of writing. We describe a comprehensive model for writing instruction in the introductory laboratory that we have used successfully for many years with different instructors. It incorporates multiple instructional elements, including the use of good and poor examples, a grading rubric, preclass questions, scaffolding student writing over multiple weeks, practice on multiple assignments, and feedback from instructors. We find that this is more effective in helping students develop technical writing skills than mere practice and feedback, an observation based on student surveys, end-of-course examinations, and tracking growth of student skills over the course of the semester. This evidence corroborates the perception among multiple instructors that it results in an improvement in students' entering writing skills, including in subsequent classes.