There is a growing number of thieves, pickpockets and beggars, but if you don't walk around with anything obviously stealable, it's quite safe and most will be more than willing to chat or give directions. For the most part Zambians are very friendly people. There is no predominant ethnic culture and Zambians are fast becoming westernised. There is however, an attempt to maintain traditional customs with the revival of ancient tribal ceremonies amongst the various tribes in different parts of the country. If any of these are taking place during your visit, they're well worth attending.
Theft however is rife in the bigger towns and cities.
Don't walk around with things you can't do without, like your passport or airline tickets. Carry minimum amounts of cash and keep it hidden or in a money belt and if possible, don't leave your car unattended. This is less of a problem in the rural areas. Zambia has mild winters and the summer days can get quite hot. Lightweight casual clothes can be worn all year round, with a jacket or jersey for early winter mornings and evenings.