The prime consideration in designing sustainable language resources is to ensure that they remain interpretable for coming generations of users. In this paper we adopt a new perspective on resource creation - securing the interpretability of data, using a case study of Ega, an endangered African language for which a small amount of legacy data is available. Basic steps to securing interpretability are to transfer files to durable media, and where possible, to convert all legacy data into XML files with Unicode character encodings. In the absence of agreed 'best practice' standards, we propose a methodology of 'better practice' to assist in the transition process towards this goal. We discuss a number of issues involved in securing interpretability of the lexicon, character encodings, interlinear glossed text, annotated recordings and nomenclature in linguistic descriptions, and describe our solutions.