Incident surveys are surveys sent to the customer after each case is closed. The advantage to this is that you can capture perceptions immediately and you can link the feedback to both the Service Group and to the Assignee. This is extremely valuable information because both rewards and training can be tailor-made based on the results. The disadvantage is that customers will get usually one survey a week and they might not respond with as great regularity. However, the advantages outweigh the disadvantages. Incident surveys are preferable to periodic surveys.
Here is an example of an Incident Survey:
It is short and to the point. Always ask for feedback in a free form field to encourage customers to openly share their thoughts. Customers will tell you things that you will never hear from anybody else. This unfiltered feedback is extremely valuable to help you improve customer service. Also, always ask if you would like a manager to call you. When you get a survey like this, it tells you the perspective of the customer service organization. When the customer reads this they will think, "Wow, these guys actually would have a manager call me, if I ask them to." Many will not request a call. Those that request a call will tell you much more then you will ever get from a written survey. Are you ready for these gold nuggets from customer who care enough to want to have a call? Ask probing questions and "peel the onion". See through any emotion and find the "signal" in all the surrounding "noise" and you are on to becoming a master in learning how to get actionable feedback which can be used to effect change in your organization.
Here is a great White Paper on Implementing Service Level Agreements. See https://www.givainc.com/wp/it-help-desk-software-cloud-whitepapers.cfm