Tummy tuck etc... how did you go about getting it approved by your ins.?

I hear a lot of people talking about getting plastic surgery for tummy tucks etc. and I was wondering how in the world you go about getting that approved by your ins. if it would be a cosmetic type of surgery? What do you tie into this surgery to get it approved? I already had my gallbladder out so that won't work. Hopefully I won't have to have any additional surgeries but just in case....