After you installed Google Gears, you can work as you normally do on your Google documents. You will see a link at the top-right of the document named Offline. If you have just installed Google Gears, when you click offline, it will prompt you with Gears security warning. Select the I trust this site checkbox, and click Allow. You'll see a dialog-box asking if you wish to create any shortcuts for Gears. After you have selected your shortcuts, Google Gears will synchronize all your content with the server.
When you are working on your documents while connected to the Internet, you should see a green sign at the top of the window which shows you are online. If you're working on Google Docs on the Internet but you don't see the green sign, either Google Gears isn't installed, or its not working correctly. Try installing or reinstalling using the directions above.
When you go offline either purposely, or because you lose Internet signal for some reason, the green symbol will turn grey showing that now you are working offline.
In offline mode, Google Docs downloads a copy of the document you are working on your computer. You can work as you normally do. You don't have to bother with saving the document; Google Docs does that for you. When you go back online, Google Docs, with the help of Google Gears, seamlessly synchronizes all the revisions from your document with the document online. You will never have to click any buttons, save any documents, upload any files or manually update the online version. Everything is taken care of by Google Gears.
Google Docs had already achieved popularity due to its capability of letting multiple users collaborate on the same document in real time. By providing offline access to Google Docs, users everywhere are raving about the convenience the offline feature provides. Why wouldn't they? Now we can work on our documents when our Internet connection conks out, when we are on a plane or in a foreign country with bad DSL. The possibilities of using Google Docs offline are endless as users worldwide are discovering!