Use the same maps
One other thing that came up recently when making and using tracks. Use the same map in MapSource that you have loaded in your GPS. Roads and trails that are shown on two different map packages won't be displayed in exactly the same place on either map. They will be generally close, but it is unlikely they will be exact. Quite unlikey, actually.
City Nav has pretty good back road coverage in my area, but it doesn't match Topo or Roads & Rec in the fine detail. Keeping a detailed track record with a gpx file (if your gps does that) is a good way to learn which of your maps agrees with the actual roads the best.