Determine what fish you're trying to catch. The size of your lure will depend on the species of fish you are targeting and the body of water being fished. For areas with large, aggressive trout and bass, use large lures. When targeting smaller pan fish or trout, choose a smaller lure. If the water is calm it is beneficial to use a small lure. This will lessen the impact on the water and help prevent spooking the fish.