If you cast out the line and there's nothing there to bite it, you're suddenly in very bad shape. Thankfully, the generous designers of Sega Bass Fishing built in an easy way to spot fish before you cast. Take a good look at the surface of the water, and you'll see shadows of the fish beneath the surface. You can even judge the size of the fish from the girth of the shadows. Look for rich concentrations of fish before you cast the line.
Lure selection is just as important as finding fish in the first place.
Those helpful shadows aren't present in Original Mode. When you're looking for a place to cast in this mode, you're on your own. On the other hand, unlike in Arcade Mode, you can control where in the lake you fish. That's important, because the fish tend to migrate around in response to various conditions. These include the time of day, the water temperature, and the sky conditions.