I use free software named Tyre to plan my trips. It uses Google Maps as a base. Any trip planned can be uploaded from the software through a PC into either Garmin or TomTom. Once in the GPS it is important to review the trip and make sure the GPS's programming did not change the route in any way. A quick addition into Tyre of more waypoints to force the route (I do this to avoid known low clearances) to go how you want it to go and re-upload. It is free and simple to use. I do extended trips with different routings stored on the GPS as pre-planned routes so that I can start and stop with different planned stops on the trip.