Well-Formed Business Process Diagrams
The following characterize a well-formed business process diagram:
- There is a start and an end event. 
- Each split is matched with a join. 
- A given input message/event is received by only one process/task.
- A given output message/event is produced by only one process/task.
- Processing of an input message/event is started in the process/task that receives the input.
- An output message/event is generated at the earliest point possible and not passed to a later process/task.
- Each process/task must have at least one input or one output message/event.
- All input and output messages/events are at an atomic level. No composite messages/events are used.
- Use parallel processes/tasks whenever possible.
- Process/task names should be in verb-noun format. An example is “pay invoice.” 
- Each task should be atomic in that it cannot be decomposed further.
- Assemble processes based on frequency and affinity. High affinity is define as having 1:1 links. This technique clusters steps with 1:1 links and separates those clusters at the point of 1:M or M:1 links. 
- Look out for orphan tasks. 
The Decomposition Matrix∞
on this site generates diagrams that meet this criteria. You do, however, need to provide the naming in verb-noun format yourself after the diagram is generated.
 Business Process Driven SOA using BPMN and BPEL∞
, Matjaz B. Juric and Kapil Pant.
 Workflow Modeling∞
, Alec Sharp and Patrick McDermott