Using the Precedence Diagramming Method
The first step in drawing a precedence diagram is to determine the dependencies among the activities in your WBS. A good way to do this is to put the title of each activity on a small piece of note paper. Take all the notes and stick them on a large piece of paper or on a wall. Along with members of the project team, work through all the dependencies, putting them in their correct order. You will probably change your mind several times and move the notes around. When the activities are in the correct order, draw arrows between them denoting the dependencies. This gives you the basic layout of your precedence diagram. Take the time to ensure that the project team agrees on the layout of the project activities.
When you have the basic layout of the diagram, write the estimated duration of each activity in the middle of its box under the title.