What is the best way to treat cervical spondylolisthesis?

Depends. Neck pain is best treated with therapy, exercise (isometric, aerobic), sometimes medication. If there are nerve symptoms (numbness, tingling, weakness, pain) in the arms, other treatment may be needed.
Sometimes surgery. If neurological symptoms are present and progressive in spite of conservative treatment, then surgical treatment could help.
Depends. This depends on the severity of the misalignment or if there is instability. Mild disease can be treated with cervical stabilization, posture correction, strengthening and range of motion exercise. Medications and cortisone injections may facilitate physical therapy. Severe disease may require surgery.