Salvador’s bus station is 8km east of the city center. A taxi to Cidade Alta or Barra runs R$25 to R$55, depending on traffic.
Buses (R$0.70) marked ‘Praça da Sé’ go to the center from in front of Shopping Bahia (previously known as Shopping Iguatemi), just across the footbridge in front of the bus station. Going to the bus station, any bus that's labeled 'Shopping Bahia' or 'Iguatemi' will get you to the vicinity.
Public buses crisscross the city; particularly useful to tourists are those that run between Barra and Praça da Sé (R$3.70).The destinations are clearly labeled on the front of the bus.
Note that passengers board the bus through the rear door (and pay the attendant seated there), then disembark from the front door of the bus (near the driver). There are two main city bus terminals in the center that can serve as destinations or transfer points: Terminal da França in the Comércio, and Lapa, behind Shopping Lapa and Shopping Piedade. If heading north to the Igreja NS do Bonfim, catch a bus from the stop at the base of the Elevador Lacerda.
Taxis can be taken at meter price (legal) or negotiated, but you might not get to choose which. Uber is also available.