If you are new to the GBBC and plan to do it this year, check out the how to participate page to learn how to record birds and report your observations. The basic idea is that you watch and count birds in one location for at least 15 minutes and then enter the sightings through a form on the GBBC website. The location can be your backyard, out of the window at work (if your office has a window), in a local park, in a nature preserve, or in some other location where birds might show up. Counts can be conducted as a stationary count (like out a window) or a traveling count (like a walk through a park). Each count should be recorded on a separate checklist.
The GBBC website has some useful resources. First, there is a page to learn more about identifying birds. Here are some highlights from the 2011 GBBC. You can download or print a checklist for your zip code, based on what birders there reported in past years.
I encourage all readers to submit at least one checklist during this year's count.