Share 'How do YOU wrap?'

I've never done any wrapping of any type so I thought I might pull out my motorcycle and play with the gastank and plastics on it.   My question to you who do wrap is..how you you start your layout? Do you use special software, do you have images of the specific vehicle parts(fenders, doors,hoods, etc), do you simpley measure the parts to find the total surface area?   Any input would be apprecia…