The really cool thing was that we were both able to work on the same spreadsheet at the same time. Any changes he made to the spreadsheet were immediately passed to the copy I was using and vice versa. In fact, I could even see the cell on which his cursor was currently located and he could see mine. So how do you share a document?
Start by clicking the "Share" button usually located in the upper right corner of your document or spreadsheet.
You can add the email addresses of folks with whom you want to collaborate and, by clicking the "Can Edit" link, indicate what privileges they have with the document. Most likely you'll want to leave the default alone since it will allow them to change the document.
Check the "Notify..." box and they will receive an email notifying them you have set the document up for collaboration and giving them a handy link to click to go directly to the Google document. Don't forget to click the "Share & Save" button.
That's it. You will all be able to view the document at the same time and make changes that everyone will see as soon as they are created.