1. Don't Light up in Public!
According to Inside the murky world of Nairobi's smoking zones | Tobacco industry | The Guardian
The Kenyan government has banned advertising, marketing, and smoking in public places, and in Nairobi, they are especially strict about it. In the city center is a wooden shed that is the only place where you can smoke. Lighting up n the street could earn you a fine of up to $485 or you could even be arrested.

2. Don't Cross The Road Without Looking.
According to Things They Don’t Tell You About Visiting Nairobi (theculturetrip.com)
Traffic lights and road signs are pretty much taken as suggestions rather than obligations. Some claim that this is because of confusion between the green light meaning "go" for cars and the green man meaning "go" for pedestrians.
Always look both ways and never assume that you have right of way.

3. Don't Cross The Road Whilst On The Phone.
This isn't just because using your phone whilst crossing the road is distracting, in Nairobi, it is actually illegal too. According to Things They Don’t Tell You About Visiting Nairobi (theculturetrip.com)
It is illegal to use your phone whilst crossing the road and doing so could earn you a hefty fine.

4. Don't Take Shortcuts Through Alleyways.
According to    • Video  
Although Nairobi is generally a safe place, you are a tourist and therefore a potential target, especially if you end up in an alleyway that the locals know is best to avoid.
Stay on the main streets and shopping areas, take your time and relax, it is better to take a bit longer to get somewhere and to arrive with all your belongings.

5. Don't forget about M-Pesa
Nairobi is big on Mobile Banking and M-Pesa is king.
Basically, as you would with a pay-as-you-go phone, you top up your phone with credit and can then transfer that credit to other people or businesses using pin-protected SMS messages. In 2011, M-Pesa had 17 million users in Kenya alone, and nowadays it's used by everyone. If you don't want to be carrying around a lot of cash with you, get M-Pesa.

6. Don't forget to get your Visa.
   • The DON'TS of Visiting Kenya | wish i...  
You used to be able to get apply for your visa once you arrived in Kenya, as of January 2021 you have to have your visa before you leave your home country. Fortunately, it can all be processed online but is does take some time so don't think you can get it done while you wait at the airport.

7. Don't say "Jambo".
According to 23 Things to Know Before You Go to Nairobi (roadsandkingdoms.com)
People in Nairobi only use "Jambo" a form of saying "Hello" with tourists. If you want to say "Hello" and gain some respect with the locals use "Habari" which is like "How are you" or "Niaje" which is Nairobi street slang for "How's it doing".
If you're the one being asked, you can answer with "Mzuri" good, "Si mbaya" not bad or "Poa" cool. Try to learn some Kiswahili before traveling to Nairobi, the locals will appreciate it and probably be more inclined to help you and less inclined to try to overcharge you.

Get more Tips here! http://www.destinationtips.com