How can you get rid of a double chin?

Identify cause. Treatment depends on the cause. See your local plastic surgeon and s/he will be able to provide you with options appropriate for you.
Anatomy. Depending on your particular anatomy and physical property of chin tissue, you could get any or all of these: a chin augmentation, sub mental liposuction, face/neck lift, platysma muscle tightening. Non invasive or minimally invasive procedure offer limited improvement.