Guidelines for constructing Network Diagrams:

1. Each activity is represented by one and only one arrow in the network. Therefore, no single activity can be represented twice in the network.
2. No two activities can be identified by the same beginning and end events. In such cases, a dummy activity is introduced to resolve the problem.
3. Two events are numbered in such a way that the event of a higher number can happen only after the event of a lower number is completed.
4. Dangling must be avoided in a network diagram. This happens when precedence and inter-relationships of the activities are not properly identified. 5.
5. To ensure the correct logical sequence and inter-relationships, one has to answer the following questions satisfactorily:
   • Which activities precede this activity? That is, what other activities must be completed before this activity can be started?
   • Which activities follow this activity? Or, what activities cannot be started until this activity is completed?
   • Which activities can take place concurrently with this activity? Or, what activities can be worked on at the same time when this one is being performed?