A France road trip begins with a map, not a ferry timetable. Decide where you want to spend the first night and work backwards.
Choose the first night's stop first
A north-France itinerary may point towards Calais; Normandy towards Caen; and Brittany towards Roscoff. Check which arrival saves you time on the road rather than automatically choosing the quickest sea crossing.
Keep the first day loose
Driving off into France is exciting, but there may be queues before you reach the road. It's more enjoyable when you can stop for lunch, pick up supplies and settle in without watching the clock.
Look at the round trip
Where will you finish? Returning from a different port can sometimes make the route work better. Compare both sailings with your actual vehicle and travel dates.
Routes to compare
Explore the destination
A few things you might be wondering
Which route is best?
The one that lands closest to your first destination is often best.
Book a hotel immediately after arrival?
Yes if helpful, but leave a realistic buffer before anything fixed.