Open Source Intelligence or OSINT is one of the 5 types of intelligence. It is defined by Wikipedia as "Data collected from publicly available sources to be used in an intelligence context. In the intelligence community, the term "open" refers to overt, publicly available sources (as opposed to covert or clandestine sources). It is not related to open-source software or collective intelligence.
OSINT is everything from a google search to reading the newspaper. Being able to develop and fine tune this skill set can assist in day to day investigations.
Here are some OSINT Training Videos to Watch
Some tips and tricks on how to research telephone numbers which may not be publicly listed or in RMS.
Every come across a third party caller such as a suicide hotline only able to provide an IP address? This might not give you all the answers but it may help.
Ever think about using a map for some extra research? You would be amazed by how much information you can use and find by using google or bing maps. Easter Egg at the end: How to remove your home from being visible on google maps.