Strategy Management

Answer:
Developing Service Strategy requires to take various views:
- from business side
- service oriented view
- (internal) organization point of view
That implies that systematic approach needs to be taken. Strategy plan and process description will help you systematize activities. Take a look at free preview of these documents:
Strategy Management for IT Services Process https://advisera.com/20000academy/documentation/strategy-management-for-it-services-process/
Strategy Plan https://advisera.com/20000academy/documentation/strategy-plan/

Also, these articles can give you some hints
ITIL Service Strategy: What and Why of ITSM https://advisera.com/20000academy/knowledgebase/itil-service-strategy-itsm/
ITIL Strategy Plan – Are you sure you have this document? https://advisera.com/20000academy/blog/2015/05/26/itil-strategy-plan-are-you-sure-you-have-this-document/
ITIL strategy – Framing the value of services (part I) https://advisera.com/20000academy/blog/2014/11/11/itil-strategy-framing-the-value-of-services-part-i/
Strategy Management for IT Services – holding your steering wheel https://advisera.com/20000academy/blog/2013/10/22/strategy-management-services-holding-steering-wheel/