The better areas under the ice are not always marked by groups of anglers that beat you to the spot. Sometimes they are. Don't be afraid to move away from the crowd to catch more fish. Temperature, structure and current can be important factors to finding fish. Stream mouths or underwater springs can remain warmer during the winter.
Water coming from streams or even drainage ditches can be colder at times due to melt offs.
Also watch the ice in these areas. Live weeds are also good because the weeds are still producing oxygen. Don't be afraid to drill a number of holes. Try drilling three or four at a time about ten feet apart. Remember each hole gives only a small sampling of the entire lake.