Aetna Insurance Approval

I am in the process of taking various tests and gathering information for Aetna, which I heard is tough. Besides test results for sleep apnea, back surgery, etc. what other documentation really clinches the process. Did anyone use family information of sleep apnea, cancer, etc. ? And if Aetna disapproves the first time around, do people usually get approved in the end. Really need some feedback and hope. Thanks