For long-term preservation, datasets should be deposited in a data repository or archive. There are a wide array of domain repositories available, which accept data from specific subjects or of certain data types. For example, the Qualitative Data Repository accepts active citation compilations, data collections, and topic clusters. The Ag Data Commons is maintained by the US Department of Agriculture's (USDA) National Agricultural Library and focuses on agricultural data. The following websites provide directories of repositories and are a great starting point for considering a domain repository:
If no suitable domain repository can be located, University of Nebraska-Lincoln Libraries hosts the University of Nebraska-Lincoln Data Repository (University of Nebraska-LincolnDR), which provides researchers with a secure site for storage and long-term preservation of datasets that are no longer actively in use. University of Nebraska-Lincoln researchers can preserve up to 50 GB of data in University of Nebraska-LincolnDR for free. Above that, there is a one-time fee (see the University of Nebraska-LincolnDR website for details).
It is extremely beneficial to determine in which repository you will deposit your data early in your planning process. Many repositories expect data and metadata to be of certain types and in certain formats. Being aware of your selected repository's requirements will allow you to manage your data accordingly. DataONE provides best practice guides on things like deciding what data to preserve, identifying data sensitivity and what data has long-term value.