I got my bottling spigot from Northern Brewer. Their instructions say to drill a 1" diameter hole. I used the nut for the spigot as a guide on where to drill the hole, by putting it flush against the side and bottom of the bucket and then marking the center of the hole. Use a hole saw and it's easy to find the center. This way, after you initially get the nut on the spigot, the bottom of the bucket sort of "holds" the nut in place so all you have to do is turn the spigot to tighten. Does that make sense?
Primary: Delicious Beer
Secondary: Delicious Beer, Delicious Cider
Kegeratin': Delicious Draft Beer
Bottled: Delicious Bottled Beer and Cider