For a simple trip, I recommend Google Maps in bicycle mode, or the Komoot app. Both will do their best to direct you along recreation paths and roads with bike lanes, if they exist in your area. The Rails to Trails Conservancy is another great resource for car-free riding. To double-check visually, use Google Street View and think about whether you'd feel comfortable cycling on that particular road. For longer or more complex trips, I recommend the free route planner and app from RideWithGPS.