Available unfortunately only in German for now, this is an excellent overview of open data published last year by Bertlesmann Stiftung:
The Guide describes all key steps towards publishing Open Data (licences, formats, metadata, etc.). You will also find information on data catalogues, data portals and open government. It describes the different phases of implementation as well as questions and answers. If you have never heard of DCAT-AP.de, JSON or APIs, you are in the right place. This guide aims to give you the most important information in about 20 pages, and refer you to numerous further sources.
The Open Data Guide is part of a joint project: the Model Data Catalogue for Open Data in Municipalities. The Bertelsmann Foundation, GovData, the Open Knowledge Foundation Germany and the Austrian KDZ - Centre for Public Administration Research have joined forces to advance the topic of Open Data in municipalities. While the guide describes all the necessary steps towards publishing open data, the sample data catalogue (musterdatenkatalog.de) provides a better overview of which open data municipalities publish. It thus also serves as a source of ideas and inspiration for making available further data that is already published in other municipalities.
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We were just discussing their Automating Society Report, which is making a lot of waves around here - in part thanks to the new AlgorithmWatch.ch association: