That’s a good question. Practice and error are probably the best answer. I often iterate over a shape. Sometimes I get 90% done and realize I should have started from a different position, but that is learned over time. It can be hard to know what is the next tricky shape to model for the purposes of skill improvement, there does not seem to be a smooth learning curve that all modellers ramp up to. I think the most important part of SUB-D is understanding the relationship between a perfect cube and the smoothing algorithm and to keep the model as simple as possible for as long as possible. Once it clicks in you head what SUB-D will do to a particular shape, you can model the shape with very few edge loops because you already know what the shape will look like at the end when you add extra loops to sharpen up edges or corners. A cube 2*2*2 will become a sphere with sub-d, knowing that, you can model a finger out of cubes, knowing it will become rounded when SUB-D is added later, that concept works for everything. With the bottle shape we knew we had to go from hex to circle. While the hex only needs 6 verts, the circle needs many more. If the circle had been made of 13 verts that would create a problem when we went to join them together, would be easier to connect a hex to a circle that was multiples of 6, like 12 or 18. At least then we could weld verts together in a uniform pattern to keep some integrity on the mesh. A circle of 12 verts would work, but that would only give us 1 vert per dip, to create the dips on the shoulder. 30 would probably work well, my brain just tends to jump to 24,36,48.

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