As mentioned on previous posts, Nairobi is safe unless your stupid.
Take sensible precautions :-
Don't walk around at night on your own.
If you have to go out somewhere eg Carnivore, ask the hotel staff to call you a taxi and get them to negotiate the price for you.
When you return from Carnivore, ask the hotel waiters to do the same for you.
If you fancy going to a pub eg Zanze Bar on Moi Ave, ask one of the hotel askari (security guards) to come with you and buy them a couple of Tusker for their trouble.
Ideally choose a hotel / hostel that has a decent bar in it like Milimani Backpackers on Milimani Road and you won't have to leave at night.
Milimani Road, PO Box 21005, Nairobi, 00500, Kenya
Phone: + 254 (0) 20-272 4827
Mobile: + 254 (0) 722-347616
Ask for Patricia!
During the day time keep an eye out for pick pockets.
Don't wear anything that you aren't prepared to throw or give away if you are mugged.
Don't wear anything that could be thought of as expensive - even costume jewelry. - A local guy in Nanyuki wanted my £5 watch from Asda off me, coz it looked expensive! My £1 sunglasses from a UK market looked expensive to locals !!! - get the point!!!
Wear a money belt - but don't put all your money & cards in it. Put some in it, so that if you are mugged, they will think they have taken all your money from you. Keep the rest in your socks etc.
Treat all people politely and with respect. And most importantly - SMILE , YOU'RE IN AFRICA!!! :-)