Ok, even after 2 weeks I know some do's and don'ts:
Don't:
1. Never ever ever ever mention the ethnic groups here and if someone tries to guide you into such a conversation, the best reply is to say you know nothing about it.
2. Don't walk around at night, most of the town is off the roads by 11pm for good reason (robberies)
3. Many expats will tell you things are safe in the country side but that's simply not true. Don't travel in rural areas without informing several people of your journey and when you expect to return.
4. Don't take the motorbike taxis, you are asking for trouble.
Do's
1. Return greetings even from strangers as many people here enjoy simply saying hello
2. Visit a ceremony where the drummers are playing as it's awesome to see
3. Enjoy a sunset on the beach and try to see the Congo mountains in the background
4. Come with a healthy knowledge of French (or Kirundu) as English is still not very widely spoken
5. Be prepared for the mosquitos as they are very aggressive and malaria is common here
6. Enjoy the wonderful and rustic areas of the city and for the most part, Western culture is not seen as too bizarre here so you can jog, swim etc without any worries.