Most of the accommodation establishments in Botswana are located near the larger towns and cities, but there are also many secluded game lodges tucked away in the wilderness areas. In the towns it is rare for accommodation to be booked up. For the lodges it is safer to book your accommodation well in advance before travelling to Botswana. This can be done on-line or via travel agents that have the knowledge of the country. As with many safari destinations booking through an agent in your own country may work out cheaper than booking direct - shop around with different agents to get the best price.
As a rule of thumb P400 US$50 should get you an acceptable en suite room in most of the towns. In the smaller towns away from the tourist routes quality and prices will be lower.