This paper describes an approach to task analysis which seeks to identify potential sources of difficulty in the self-discovery of improved procedures by students who have been taught simpler procedures. The approach considers novices' procedures in terms of the changes needed to produce an expert procedure; the knowledge required to make those changes, and the processing demands of acquiring that knowledge, can then be determined. An analysis of strategy improvement in a relatively simple domain--single digit arithmetic--is provided as an example. (Author/RAO)