There are several routes from Adelaide, with the most direct being the Main North Rd through Elizabeth and Gawler. If you're coming from the east and want to tour the wineries before hitting Adelaide, the scenic route via Springton and Eden Valley to Angaston is the best bet.
Barossa Valley Coaches has twice-daily return services from Adelaide.
Cycling around the Barossa Valley is a popular option, with routes that can take in a few wineries. Ask at the Tanunda visitors centre or cycle-hire outlets for the best directions. The Para Road Trail is a rough bike path which runs between Nuriootpa and Tanunda and passes several wineries. Bicycles can be rented from the Tanunda Caravan & Tourist Park and the Barossa Bunkhaus Travellers Hostel & Cottage in Nuriootpa.
Barossa Valley Taxis (1800 288 294) have a 24-hour daily service that runs throughout the valley. Alternatively, you can rent a car from the Caltex service station on Murray St, Tanunda.