You don't have to be an experienced birder with perfect eyesight...even if you only know two or three species, but can spend a little time counting them, you contribution will help define the number of North American birds on these dates. You don't have to have feeders, or a yard full of birds...it doesn't matter how many species you report (there is competition among the competition-minded, but you don't have to bother with that. You can count in any location, like a city park or a particular vacant lot, if you're in an apartment with no yard. All the data are useful.
It may seem a daunting task at first (it is easier if you've had feeders out...you can just count feeder birds) but it's really not. You don't have to report every bird you see (there's a checkbox for whether you did or not, as well as one to indicate how you rate yourself as an observer.) This will be my sixth year; I had planned to use the Audubon Society's Christmas Bird Count as the big annual census on our place, but we're not within one of their defined circles...so I couldn't. This worked out perfectly for me.