I have been tasked to create a Service Level Management Framework for our company. For those who have performed this activity, can you give advice on how should I approach the implementation?

This is what I suggested the person can do:

1-Create a high-level Target Operating Model based on processes
         -Refer to APQC, Gartner, etc.
2-Derive the KPIs from #1
3-Measure/benchmark/create targets of the KPIs
        -Refer to APQC, Gartner, etc.
4-Derive the SLA Framework from the above

I havent been in this space for a while, however my guidance would be to start with the ITIL framework as it covers this topic.  Some basics to get started would be to understand how you may be able to categorise the various service levels which are relevant to your organisation.  Different service categories typically have different recovery and time objectives.  The specification of the RPO/RTOs need to be done in consultation with your business as these metrics have a direct implication on resourcing/cost/effort devoted to resolution or service recovery.