There's lots of reasons to share your data, including furthering scientific research, reducing the cost of redundant data collection, promoting innovation, increasing the impact of your research, and getting credit for your work through data citations. Sometimes grant funders, including the U.S. government, requires you to share your data. More scholarly journals are also starting to require or request that you share your data.
You also have lots of options in deciding where you will share your data, including various data repositories and even data journals. The University of Minnesota suggests considering eight factors when deciding on a home for your data:
Data citations help give credit to those who collected and shared the data while also providing transparency about where data came from and what version it is. Some of the data repositories generate citations in different styles for their datasets. If you're not sure how to cite a dataset, follow the general rules of whatever style you're using and include this information as applicable:
Some journals publish data papers, which describe a particular dataset vs. drawing conclusions from data. Many of these journals are also peer reviewed. Check out Katherine Aker's post for a list of data journals or contact your librarian if you would like help finding one.