Best practices to enforce SOA Architecture Governance:
1) Define SOA reference architecture
2) Identify the infrastructure capabilities it will have
3) Evaluate and identify vendor technologies that the SOA architecture will be built with
4) Specify management, security, reliability and availability characteristics for the SOA infrastructure.

Link to Resource: Why SOA Needs a Governance Framework

Source: Igor Khurgin, Saurabh Verma, ITWorldCanada

SOA Governance Resource Guide Section: SOA Governance Best Practices