Medial opening wedge high tibial osteotomy is the preferred surgical procedure for the treatment of medial compartmental osteoarthritis with a varus deformity. The purpose of this treatment is to reduce the load on the medial compartment by changing the alignment, thereby relieving the pain, and restoring function. However, deformity correction is mainly based on the bony deformity and this strategy can induce an inaccurate correction. The main cause of this inaccurate correction may be ignorance of the status of the soft tissue and the cartilage. In addition, inaccurate correction can be caused by improper planning, inappropriate osteotomy, and inadequate soft tissue management. In this review, we describe a step-by-step method to achieve optimal accuracy by dividing the process into deformity evaluation, determination of correction goals, preoperative planning, and intraoperative adjustment.