Zotero gives you a number of tools to organize your data. Familiarize yourself with the options available before you start organizing your records.
There are also several ways to find specific records in your library.
Create collections (folders) and use them to organize your citations. Collections can be made for subjects, subdivisions in your bibliography, or as reminders for you to follow up.
Use the folder icon (upper left in the Zotero toolbar) to create new collections. To create a subcollection, right click on the parent folder and pick "New Subcollection".
Click and drag citations into the appropriate folders. Remember: individual records can be in multiple collections or subcollections.
Also, if you select a folder before adding a record to your library, it will also add it to that folder.
There are three tabs to the right of the "Info" tab that can be used to further organize your library.
You can create one or more notes related to your record. Use these to keep track of Interlibrary Loan requests, books you have checked out, the locations where you are storing the book, storing citation information in non-Latin scripts, etc.
Tagging can help you retrieve related records. For example, if you have multiple records that mention someone important to your research you can tie these together with tags. Once you have used a tag, it will show up as an option when you start typing. This allows you to reuse tags and improve retrieval. Searching on a tag will result in a list of every record in your library with that tag.
NOTE: Sometimes Zotero brings in subject terms from the databases and adds them as tags. Don't be surprised when you find that your record already contains tags!
The related tab is a great way to tie records from the same source together. For example, if you have a book and are using multiple chapters by different authors you can add the record for the book, plus records for each book section. In the book record, click on "Related" and add a link for each chapter. This will, in turn, create a link from the book section record back to the book. In your bibliography you can use the citation for the book, while in your footnotes you would want to cite the individual chapters. Add all the records first and then link them together. As you type in the related tab, you will find the record you need.
To find items in your library that have not been filed into a collection or subcollection, scroll down to the bottom of the folders under "My Library", but above "Group Libraries", and click on "Unfiled Items".
NOTE: As soon as you move it the item to a collection or subcollection, it will disappear from the list of "unfiled" items. If you want to put that item in multiple folders you will need to go back into your library and find it there.