I have seen many a process diagram, one of the things that I have come to realize over the course of the years is just how different people model their processes. One of the things that I have noticed to be common across some of the most unreadable process models is the fact that they are a lot less structured than they should be. Boxes are thrown anywhere, lines overlap each other, there are 800 different elements on the page and the general feel of the diagram is that the process before you is the most complex task anyone could undertake. While it is true that there are complex tasks out there, and a lot of the really key business processes are also some of the more intricate ones. There are a few simple and yet very effective tricks available to a process modeler in order to help ensure a clean and readable diagram.
The technique I would like to look at here is the use of process layers. In most good process modeling notations you will find the ability to define a sub process, the sub process is often looked to as a source of reuse on the diagram … while this is true, the humble sub process is so much more than simply a tool for reuse. It is an invaluable modeling concept to enable process abstraction, it gives the modeler the ability to decide what to hide on the diagram leaving only the necessary detail for an accurate view of what is actually getting done. First and foremost you should structure your process to be readable and maintainable, using process layers you can abstract away detail of the process and leave only the things which are important to that level, I would suggest that you should consider the different layers of management you have within your business and then try to create a layer of the diagram which speaks to each level.
The ability to reuse sub-processes should be a result of the fact that they are naturally reused within the business, not something that is forced because you like reuse. Process layers will help you identify where this reuse is currently occurring, and where it can be occurring but is not right now. Process structure is so vital to the long term success of a BPM solution that it is critical for any process model to take advantage of the fundamental building blocks of good process design, one of those building blocks is process layering.