To design a new solvent extraction process, one needs to measure distribution ratios for the various components in the feed solution, determine the key components, and then develop a process flowsheet based on the criteria for the separation of the key components. By following a set of design rules based on the extraction factor and starting with the distribution ratios, we show how to develop the process flowsheet. These rules can also be used to determine the optimum organic-to-aqueous flow ratio and assess whether any of the components will be trapped (pinched) in the process.