Paul's answer is what most of us follow. The bit around Rouen can be fun as you go through the industrial bit and the traffic during the day is 'interesting', however it is not really that bad, and once you are past it, it is all fine. Just watch as you enter Rouen to note the correct exit, it is just as you leave the tunnel going south and is a sharp right hand bend back and under yourself to get the right road. It is well marked and if you follow signs for'Paris', if I remember rightly, it will get you to the right motorway. Also the bit between Rouen and Dreux is a great empty motorway, but no stopping places, so if you wish a 'break' go either before, or after. There used to be a layby (it is still there) on the way into Dreux that sold excellent chips, but the last time we passed the chippie had gone. Shame. The road across the plain to Chartres and on to the motorway is single track road, but pretty straight. It will take you about 45 mintutes for that bit.