The local currency is the Botswana Pula (BWP) which in turn is divided into 100 thebe. There are notes of 1, 2, 5, 10, 20 and 50. The coins are as follows: 1, 2, 5, 10, 25, 50 thebe and 1 pula. For a dollar you receive 7.73 BWP (December 2012).
The currencies are still not stable. It is best to consult a financial newspaper a week before departure. On the internet you can look at www.oanda.com for example. Cash in the form of dollars and euros are locally exchanged at all banks and exchange offices. The Euro is still a new currency in Namibia, Botswana and Zimbabwe so dollars will generally give a better rate of exchange.
In Botswana you you can make payments and limited daily withdrawals with a credit card. Visa cards are more widely accepted than MasterCard.