Many project managers feel the project network is their most valuable exercise and planning document. Project networks sequence and time-phase the project work, resources, and budgets. Work package tasks are used to develop activities for networks. Every project manager should feel comfortable working in an AON environment. The AON method uses nodes (boxes) for activities and arrows for dependencies. The forward and backward passes establish early and late times for activities. Although most project managers use computers to generate networks and activity times, they find a keen understanding of network development and the ability to compute activity times is invaluable in the field. Computers break down; input errors give false information; some decisions must be made without computer "what if " analysis. Project managers who are well acquainted with network development and AON methods and who are able to compute activity times will encounter fewer problems than project managers less well acquainted. Project networks help to ensure there are no surprises.

Several extensions and modifications have been appended to the original AON method. Lags allow the project planner to more closely replicate the actual conditions found in practice. The use of lags can result in the start or finish of an activity becoming critical. Some computer software simply calls the whole activity critical rather than identifying the start or finish as being critical. Caution should be taken to ensure that lags are not used as a buffer for possible errors in estimating time. Finally, hammock activities are useful in tracking costs of resources used for a particular segment of a project. Hammock activities can also be used to reduce the size of a project network by grouping activities for simplification and clarity. All of the discussed refinements to the original AON methodology contribute toward better planning and control of projects.