One tool I recently discovered is the Navionics app for smart phones. Subscription is $20 for a year. It has great contour detail like my DFs but the neat part is being able to study the lake in detail from your easy chair (or office) and mark spots that look good. Its a dynamic app so it will guide you on the water to spots you mark.
If you have an active Navionics map card in your DF you can transfer data from phone to DF.
The app is really handy when fishing on a friends boat because you can save and share waypoints via the app.