Plan your route
For specific route instructions you should purchase a good Road Atlas and/or you may like to visit this site:
Not only can you choose the route to avoid motorways or toll roads, you will also be provided with the total distance of the journey together with the estimated time it should take.
Details will also include a list of the distance to each junction, road numbers and all other route information required to avoid getting lost!
The Via Michelin web-site is another fabulous source of information, plus it also provides information on toll costs when you enter your route.
Of course if you book a car with GPS, while you should still take a road atlas (no GPS system is ever 100% accurate), a lot of the detailed planning is done for you as you drive!
Tourist Board web-site addresses:
Czech Republic: http://www.czechtourism.com
Slovak Republic: http://www.slovakia.org/tourism
And for a list of UNESCO World Heritage sites: http://whc.unesco.org/pg.cfm?cid=31