I use a simple customer survey... I send it out twice in a 12 month period..
I used to only send it to our top 20 customers, but then I thought, why not the others.. maybe hearing what the other customers have to say would tell us why we are not getting more business.
The survey lists the usual.. product quality, product packaging, customer service, etc. There is a rating 0 - 5.. and then a section asking what we can do to better serve the customer. This has proved to be benefical information.
We review each and every returned survey at our Management Council Meetings... It is a great way to show all of management what the customers think of us, and also a great way to collaberate a way to fix the issues they point out...
I put all the data together myself.. not really much support if you exclude management council, but it works really well