You can lay the diagram out in the following ways:

This page explains what each layout does, and the advantages and disadvantages of each layout.

Circular

The circular layout lays the objects out to form the boundaries of circles, with connections that cross the centre of the circle.

Hierarchic

The hierarchic layout organizes the objects in a hierarchical structure, where objects are placed in tiers above the objects they reference.

Orthogonal

The orthogonal layout places objects so that the lines between objects are as close to vertical and horizontal as possible.

This is best for diagrams that don't contain many objects.

Smart organic

The smart organic layout links objects into sets of clouds or lattices. 

This layout is good for grouping related objects together.

Balloon tree

The balloon tree layout groups related objects together in balloon-like clusters. It is the default layout.

This layout is good for grouping related objects together, and is suitable for diagrams that contain lots of objects.