Hmm... Will you have a local guide? Someone to steer you out of bad areas?
I was there for a month in 2007, but we were with a kenyan friend the whole time. We took public transportation everywhere (which was pretty crazy) and Matatus (which were really crazy). If you're white, expect to get asked for money pretty frequently. There are some people who just go around asking anyone who looks like a tourist for money.
Oh if you're buying a wooden statue or something off the street and the seller says it's ebony, it's not ebony. And usually you can buy cheap tourist goods for about 1/10 of the original asking price. You just have to be willing to walk away.
I don't know what else to say...Kenya is a tribal country. I think there are 42 tribes, and even in urban, professional centers like Nairobi, people still identify pretty heavily with their tribes.
That's all I've got. Maybe you could ask a more specific question?