Trolling is always a good way to catch fish as well as check out a lake's shoreline and map the bottom structure as you go.
But if there is a time of year that casting shorelines can be very productive it is early season - May thru Mid June. Fish are seeking warm water at this time so look for spots in the lake where the water warms first. Start shallow looking for dark bottoms, river and creek inlets, windy shores where the warmer surface water is "piling up". Shores with a lot of downed wood tend to be dark and warm water faster and also provide a place for fish to hide.
This would also be the time of year when you could find fish fairly easily without a depth finder. Especially if you are not fussy about what kind of fish you want to catch. You might find a thermometer useful at this time of year. When you find a particular area that holds fish, check the temp and then look for other similar areas. Smaller lures worked more slowly might also be more productive.