A) ITIL: FTW, seriously. ITIL will explain how your processes *SHOULD* work. Incident and Problem will most likely be your focus. Maybe a little Inventory Mgmt and Configuration Mgmt stuff too.
B) BPML/BPMN: Diagram those processes out.
A) My company, FrontRange (www.frontrange.com, sells a product called HEAT for service desks and a product called ITSM that is ITIL centered.
B) You can also look at Remedy (www.numarasoftware.com) and Magic (www.kace.com). As far as I know Magic is not ITIL, but Remedy can be. However, Remedy is very expensive. Magic is the cheapest of the bunch, but not very configurable.
Good luck in your search!
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