This document summarizes lessons learned from open government data projects in Spain and internationally. It discusses the varied approaches taken in different Spanish regions, common concerns raised about open data, and lessons regarding organization, finances, and technology. Key lessons include starting small, identifying champions, performing cost analyses, adapting to existing systems, and addressing concerns about privacy, legal issues and complexity through improved standardization and capacity building. Overall open data projects are increasing and providing success stories, but the full ecosystem of social, economic and political factors must be considered.