The theory of planned behaviour (TPB) is a widely used theory in behavioural analysis. It incorporates social, cultural, psychological and economic approaches into behavioural analysis. The authors of the theory of reasoned action and its extension, the theory of planned behaviour have recommended that it is appropriate to conduct an elicitation study to identify the final sets of salient beliefs in the TPB analysis. Even though the TPB is based on salient beliefs, researchers have paid less attention in this regard. In order to identify final set of salient beliefs for TPB analysis, Ajzen and Fishbein (1980) have suggested three rules. This paper compares the three rules suggested by Ajzen and Fishbein (1980) and an alternative approach was suggested. The paper analyses the beliefs of farmers in Sri Lanka in respect to the decision to adopt new technology. The findings showed that the three rules suggested by Ajzen and Fishbein (1980), lead to different sets of salient beliefs for TPB analysis. Therefore, an alternative approach was suggested which is a trade-off between salient beliefs that fall into the final set and beliefs that are foregone. The suggested approach is strengthen by computing the product of the “belief strength” and “outcome evaluation” (expectancy value method) for each belief mentioned. It provides more accurate index for eliciting the most significant salient beliefs for TPB analysis.