Behind every successful BPM implementation, you will find a good project plan.
There has to be a reason for implementing a business process management solution. The problem that you are attempting to solve will be extremely annoying. You will have decided that you just can't take it anymore and it needs to be fixed. Or the cost of the problem just keeps mounting up and it needs to be fixed.
At a high level, I like to break down a BPM project into 4 major steps: Analysis, Design, Construction and Implementation.
I see the analysis step as the real key. It is like the foundation to a house. If it isn't done right, the building of the house will not go smoothly. You will see many change requests.
The analysis is where the communication begins. Terms will be defined, the problem areas will be clearly delineated and the customer will describe their idea of a successful outcome.
As with any project, miscommunications are something you try hard to avoid It can be the difference between success and failure--it can be the difference between a happy customer and an unhappy one.
Hopefully, when performing the analysis, you will find a person with some experience (so they know what questions to ask) and is also a good listener (so they can really hear the answers given). You would like for them to confirm their understanding of the customer's needs.
Using these skills, they can successfully pass requirements to the "solution designer" so that the solution can be properly configured and/or coded.
Obviously, if the world were perfect and there were flawless people, the first cut of the solution would be correct and make the customer happy. Since we are only human, we can only do the best we possibly can (and hope for some luck along the way).
What has been your experience?