The moment of choice, when a decision option is identified as being preferred, is a key stage in a decision-making process. Some explicit or implicit mechanism, be it optimising, satisficing or a combination of the two, is required to make a choice. Dependable decision-making requires an appropriate choice mechanism, but the process and criteria by which a choice mechanism is selected are seldom addressed. A contingency approach to choice is proposed in which a choice mechanism is selected according to the characteristics of the information available and the meta-level constraints and objectives of the decision-maker. Information used in the choice is characterised according to the extent and type of uncertainty. The importance in effective decision-making of meta-level requirements, for example for inclusive and transparent mechanisms, is discussed. Normative and fuzzy choice mechanisms are cast within a generic framework of choice mechanisms. A new theory of choice based on interval probabilities is introduced for use in some situations where existing theories of choice are inappropriate.