Lots of fish have been planted in the last 2 years. Ask other fisherman where they have had luck and what they have been using for bait, trolling depths, etc. Ask other bait shops. Gather Information - Little things make a big difference. The size of the lure, size of the line, time of day, etc.
Some lures work on sunny days, others are better on cloudy days.
Keep notes - on what worked and what didn't. If - successful stick with it, if unsuccessful experiment. For example, change lures, move spots, change depths, change bait. Read - Pick up books and articles on the specific lake you are fishing. The more you fish a specific body of water the better you will do, however you must adjust to water and weather conditions, put in the time and experiment.