Ravensburg has a train station with direct services to Ulm (about 45 minutes), from which you can connect to Stuttgart and Munich. There are also direct regional trains to Friedrichshafen on Lake Constance (about 30 minutes), making it easy to combine Ravensburg with a day on the lake. From Stuttgart, the journey with a change at Ulm takes around 1 hour 45 minutes.
By car, Ravensburg sits just south of the A96 motorway between Munich and Lindau, and is easily reached from the Allgäu, Bregenz, and Lake Constance. A B&B or hotel in the old town avoids the parking question entirely — the historic centre is pedestrianised and best explored on foot.