I am not an ice fisherman but I thought I would post this informational piece I picked off the web since many of us will be trying for the ice fishing derby, perhaps some of us would be ice fishing for the first time.
Ice Thickness for Ice Fishing
Less than 4 inches ? please don't go ice fishing. There is no reason to test the newly formed ice at this time. If you still proceed out, wear a life jacket, use ice picks in case you fall through and need to get out, and use a pole to poke the ice in front of you.
4-6 Inches ? Ice fishing, foot travel in single-file lines, and small spaced seating on the ice should be safe, presuming the ice is clear and clean. If you've gotten a lot of snow or had some recent warm spells be VERY careful for weak spots.
The recent heavy snow pack can actually weaken the ice by insulating it from the colder air and allowing the relatively warm water to erode the ice from underneath.
Good luck,
Tom