How soon should you book a reservation. Its only three weeks away and I still haven't done so yet. We are going to need to eat that day.

Depends on where you want to eat and where you are. Some top restaurants are surely fully booked by now. Others you might be able to get in without any reservation. French Laundry (if it's open) forget it. Waffle House on the Interstate -- probably no problem. I guess I don't get your question without more specifics.

I am taling Orlando International drive. I know there are many resturants there.

Check out opentable.com for reservations on Christmas.

Next time, if you are more specific in your post title then you are more likely to receive helpful responses. Such as, "Christmas dinner in Orlando/ when to reserve" or something similar.