Botswana's HIV infection rate, estimated at 24.1% (http://www.unaids.org/en/...), is the 2nd highest reported in the world. Exercise regular universal precautions when dealing with any bodily fluid and remain aware of this high rate of infection. Take precautions accordingly. Wear rubber gloves when dressing someone else's cut, even if they are a child, and obviously NEVER, EVER HAVE UNPROTECTED SEX. If you form a serious relationship, consider both getting an HIV test before taking things further.
The northern part of Botswana, including Chobe National Park and the Okavango Delta is in a malaria zone, so it is advisable to take the relevant precautions. Seek medical advice before travelling to these areas.
Water in urban areas is chlorinated, and is drunk from the tap by the local population. Still, short term visitors with sensitive stomachs may feel more secure drinking bottled water. Outside of urban areas, the water is untreated and straight from the borehole and poses a slightly higher risk to the traveller.
Citizens of 67 countries, including Australia, Canada, Netherlands as well as other EU countries, Singapore, Malaysia, Hong Kong, UK and US, do NOT require a visa. For citizens of other nations, a visa must be obtained prior to arrival. As of February 2009, a visa from the Botswana embassy in Washington costs US$107; for more information and a complete list of countries which do/don't require visas, see: (http://www.botswanaembass...).
The official languages of Botswana are English and Tswana. Kalanga is spoken near the Zimbabwe border areas, and is similar to Shona.
The language of business in Botswana is English and most people in urban areas speak it, although in the more rural areas many people do not speak English, particularly the older generations. The primary indigenous tongue is Tswana, and is the first language of the overwhelming majority of the population. It is not difficult to learn basic greetings and such, and using these in conversation will make people very happy.