With snakey staves, it is crucial for me to get a good center line first. If the stave has been split, the grain was automatically followed. That means the centerline is right between both split sides of the stave. Take a pencil and slide your fingers along the side of the stave. Keep the distance between your fingers the same, and a centerline with a uniform distance from the side will appear. This centerline does not indicate where the string will be. That means the string may currently track off the handle. If you're lucky, the string bisects the centerline in the handle. Snakes in the limbs are great, but you ultimately want the string in the center of the handle. Heat corrections may be necessary to get the string in the center of the handle.
Once the centerline has been established, you can mark your width taper on the back of the stave. Make a small sketch on what your desired width taper looks like, for instance a pyramid-taper from 2" at the fades to ½" nocks. In that case, mark the handle first (still with the centerline as the center of the handle, even if the string does not bisect the handle yet). Mark the fade, so 1.00" each side from the centerline. Mark the nock, so 0.25" from the centerline each side. Mark midlimb (distance tip to handle fade) 0.625" from the centerline each side. Mark quarter limb (halfway between the two previous points) etc. Once you've accurately measured some points on the limbs, you can connect the dots. If you mark every 6" of limb length, you can just connect the dots free hand. Make sure the bottom and top limb are equal in width lay-out. Double check this before you take any wood off. If you accurately lay-out one limb, you can easily use these measurements for the other limb.
A drawknife is the best tool for snakey staves. The knife will automatically follow the grain, so it will guide you along the grain. Get close to the width taper you've just laid out on the back of the stave, but do final width taper with a less aggressive tool.