Zotero allows you to make collections of citations so you can keep everything organized. To create a new folder, click the folder icon with the plus sign at the top left. 
Collections can be renamed for organization (e.g. by class or project). By right-clicking on a collection, you can choose to delete the collection but keep all the items in your main library, or you can delete collection and items together.
Similar to the Smart Groups function in EndNote, Zotero's tags can be a useful way to organize your references and find them quickly when you need to. To add a tag, select an item from the center column, and then scroll down to the "Tags" section of the right column. Type in each tag you want to add, and then hit enter. Some sources will have subject terms included as "tags" in their metadata. In a previous version of Zotero, options for "notes", "info", and "tags" were organized in a horizontal menu. In the latest version of Zotero, you need to click the caret next to an option to minimize or maximize it.
A bank of all your tags is visible on the bottom left column, and if you click on one of those tags, it can bring up a list of every item you've tagged with that word. This can be a useful way to locate all your references about "Mindfulness." Another convenient use of this function is to tag all articles you need to request through Interlibrary Loan with a tag like "ILL."
