If you are at all familiar with the body of water that you are fishing it helps too. Areas with current are usually bad earlier than where the water is still. An example I will give is on Chassell Bay. A few years ago I went out toward the end of the season. I was fishing on the south side of the point that seperates the bay from the main lake. When I drilled the first few holes there was around 3' of ice. I walked about 50 yards further down the point and my auger cut the hole almost immediately. The ice was only 6" or less there. The current from the cut from the Sturgeon River was eddying around that area and the warmer water coming in from the river was eroding the ice underneath the surface. If you have lived by, or at least looked at, a lake over a number of years you will recognize a pattern where the lake usually opens up in the same places first every spring.
And somebody mentioned checking with a spud: this is a good idea but it isn't infallible. I followed somebody else onto Keweenaw Bay a few years ago. I was checking every few feet with the spud and still dropped through the ice even though the spud didn't indicate any trouble. Be careful and stay safe! The fish aren't worth drowning over.
