If you're regularly using more than one computer in your research, Zotero's sync feature can keep your library up to date on all of them. Zotero can store a copy of your library on the Zotero.org server and check it for updates whenever you open your library on a different computer. All your computers must be running the same version of Zotero for synchronization to work properly.
Step 1: Enter Zotero Account Information in Preferences
First, set up a (free, of course) Zotero.org user account. Then:
Repeat this configuration on each of your computers. Any updates you make on one of your computers will be reflected on the others. This even works to synchronize your library among Windows, Mac and Linux computers.
Step 2: Sync Your Library
Once you have your Zotero account information inputted in the preferences area of the Zotero application, click the green arrow to begin the sync process.
As an alternative to manually syncing across computers, you can export your Zotero library and transport it portably with a flash drive.