Is there a guide or an introduction of some sorts to open data, indicating to a beginner how and where he or she should go about trying to find interesting datasets?
Open Data looks a bit like a jungle at first but you'll find tons of awesome data and tons of ideas to create stuff with it!
The first questions would be: are you searching some particuliar data or are you just curious? what do you want to do with those data?
Then I would say:
- the first step is find some data near you. The OKFN runs a service called Data Portals where you'll be able to find your government/city open data portal (eg. City of Paris, France). Usualy data are in CSV/TSV, XLS so you can explore them with a Spreadsheet Software.
- you can check plenty of other sources with thousands of open data websites: OpenDataSites or this Quora Q&A.
- then you will probably want to do something with those data. Depending of your skills, time, and what you want you can try some data science library like R or Python, some data visualization (personnaly I like d3.js), some map creation (I heard that Mapbox was cool but I've never tested it).
- the next step will probably be some global data like data from the UN or the World Bank. It will be a good lesson on how it can be difficult to access some data even if they are open :)
- you'll search some data for hours, ending here to ask the community
- you'll find out that even if there are more and more open data, there are still a lot of data difficult to find and not open. That will be a good time to first learn more about scrapping (eg. with Scrapy but every language has its library or with stuff like Import.io), and second, make friend with people, NGOs, companies that are fighting/working on making Open Data bigger and bigger. You'll easily find those people/org online ;)
- finally you'll probably want to be curious about stuff like Semantic Web and Linked Data.
Then, I hope you will have seen the huge power Open Data gives to people and if you work at a company/organisation that has some interresting data you'll wonder how to open them easily. There will be a lot of informations online, some guides too. Some ready-to-go platforms exists, some Open Source, some not like Socrata or OpenDataSoft (DISCLAIMER: I work for the latter) and plenty of others.
I hope it'll help you. Don't forget that your favorite search engine will be a direct access to the data you want in most cases.