Well, if you want to start your bike ride on an appropriate place, then start at the Ski and Bike Centrum Radotín (http://www.skiservis.cz/). They will let you park at their parking lot and you should definitely visit their warehouse (especially if you want to drop a lot of money on the next bike of yours) or have a lunch at their cafeteria. You can also test your biking skills on their test bump road.
From there you will ride along Berounka river on a nice bikepath up to a bridge in Dolní Mokropsy (2). If you are scare of heights, crossing this bridge may give you goosebumps as the bottom of the walkway is nicely see-through. Nice and easy path will turn into an uphill and between 3 and 4 it will turn to the super-uphill. Make sure that you change your gear well ahead the sudden turn to the right after the bus station. You can also follow the road to point 4 – longer but much less steep.
After riding down to very close to the highway, you will be riding through nice forest which may seem like a forest in some of Czech mountains. The stretch of the path between points 6 and 7 will surprise you with some ups and downs which you would not expect here. When you arrive in Lipany, pay good attention to the downhill road between points 10 and 11 – we rather walked our bikes for a little bit.
After riding through the big golf course and crossing another bridge you will be back where you started. It is about 30 km with 324 m elevation gain – very easy with the exception of points mentioned above.