Baden-Württemberg has an excellent rail network, serving even quite remote areas. Especially rural villages are served by busses which generally leave from main train stations in larger towns and cities.
Of course you can always use your car. If you are travelling in the Black Forest or the Swabian Alb during winter, bring snow chains as some smaller roads may not be plowed frequently enough. When travelling on the Autobahn, the same precautions as everywhere on German high speed roads apply: If you're not willing and prepared to drive consistently above 80 mph 130 km/h, stay on the right. Make room for people trying to overtake, use your common sense, don't drive faster than you can think.
