I really wanted to capture a classic golden-age look to the characters so my first port of call was to find out how they were designed and constructed. I went to John K's blog because he has an extensive amount of articles on the subject.
What creates the feel of a character from this period is that characters are constructed to be never perfectly on model. Characters are designed with circles, pears and tubes. They are constructed out of soft curves. This gives the characters a three-dimensional feel. It also allows the animators to practice animation principles from them. Characters were design to allow the animators to squash and stretch the characters to create the expression they want. Use pears and spheres to create simple organic characters.
This knowledge has given me the freedom to push the shapes and not worry if the character is on model or not.
Here are some examples.
Here are a couple of scans from Preston Blairs book, from John K's blog.
Here are some drawings I have done based of of these.