Pick up the phone before you pack your auger. Fish and game departments, sporting-goods stores, fire departments, and sheriff's offices can give you local ice conditions. They also can alert you to the locations of springs or inlets that may be covered by thin ice. But don't limit your questions to thickness alone--it's just one factor that contributes to stability. Ice that forms after a hard freeze in December will be far stronger, inch for inch, than late-winter or spring ice, which will likely have thawed and refrozen.