If you are planning to develop some new code for Sage, design is important. So think about what your program will do and how that fits into the structure of Sage. In particular, much of Sage is implemented in the object-oriented language Python, and there is a hierarchy of classes that organize code and functionality. For example, if you implement elements of a ring your class should derive from sage.structure.element.RingElement, rather than starting from scratch. Try to figure out how your code should fit in with other Sage code, and design it accordingly.
See About this document... for information on suggesting changes.