The importance of project evaluation and network diagrams in the selection of viable projects for a firm is emphasized. Managers must use project evaluation methods to determine the viability of a project, as simply relying on increasing cash flows does not guarantee success. Additionally, network diagrams are crucial in determining the sequence of activities, which can help control costs by completing projects on time. In conclusion, managers should utilize both project evaluation and network diagram techniques to make informed decisions when selecting projects for their organization.