ITIL is published in a series of books published by the U.K.'s Office of Government Commerce, each of which cover a wide range of IT management topics. ITIL gives a detailed description of the best practices of a number of important IT processes with comprehensive checklists, tasks and procedures that can be tailored to any IT organization.
ITIL is in its third revision now after its initial development in the late 1980s. ITIL v3, published in May 2007, is comprised of 5 key volumes:
1. Service Strategy
2. Service Design
3. Service Transition
4. Service Operation
5. Continual Service Improvement
While ITIL covers a wide range of topics on IT service management, the most widely used portion of the library is the Service Management set. The service management set covers topics such as service desk operation, incident management, software asset management, change management and service level management. All of these are important areas that, if implemented properly, can provide a much more stable and secure technology environment.
In short, any service vendor that is committed to providing ITIL training and process development will most likely be focused on providing a superior level of service to you and your organization.
Finding a service partner that fits your organizations needs is challenging. Talking to their current clients will give you a sense of how well the vendors works with others and how they might fit your organization. Looking at their certifications and commitments to providing excellent service will tell you whether they have clear understanding of what it takes to be a true partner for you and your organization.