The ASP should have a defined specialty. Moreover, the services the ASP offers should be equal to or greater than those of the application vendor. Accepting anything less would be a waste of your time. Security and support are other major features you must consider. Be certain any ASP you select has appropriate security in place.
Some ASPs offer fully integrated solutions, while others provide solutions on an as-needed basis.
ASPs are now more customized and full-service than in the past, providing frequent upgrades, new drivers and help files. But they still vary widely in terms of service level and customer support. Be sure to agree upon a statement of services that identifies everything the ASP will give to you. Talk to your users about what they want and need. Present your outsourcing plans to them and get their feedback.