Bureaus generally give better rates than the banks, especially for cash, and have a faster service.
Cash advances on a credit or debit card can be had in Lusaka, but don't expect to get cash for plastic in other towns. There's no black market worth bothering with, and most street moneychangers will rip you off. Tipping is technically illegal, but of course still welcomed. When shopping for crafts and souvenirs at curio stalls, or when buying some market goods, bargaining is common and expected. Bargaining is not common in shops.