Most of us know not to stare at a wild monkey or baboon because it is considered to be threatening to them. Those who have had a relationship with specific individuals in the wild will know that in time, one is able to look into the eyes of the non-human primate as they do into yours, simply because you are no longer considered a stranger.
When you come across wild monkeys or baboons while out walking, it is important to turn your eyes downwards, remain calm and walk slowly. Don't walk towards them or face them.
If you look at this video clip you will see me purposefully walking past a wild male baboon to illustrate the respect the baboons here have for us. The baboon turns away, showing respect for my personal space in the same manner that a lower ranking individual in a troop will do when a higher ranking individual walks towards the other.
Most wild baboons know humans as individuals and do not generalise about people.
However, there are some baboons in other areas who have learnt to generalise about people and have been forced into a number of situations to try and get food where the baboons have learnt how scared people get when they intimidate them. They know that all it takes to get food is to frighten someone enough and the food is accessible. Their intention is not to harm the person but to get the food and with a bit of common sense the situation is easily divereted.
In these cases the baboon appears very menacing to the average person. Try not to panic, back away and if you are scared, drop the food that the baboon wants. If a baboon snatches your bag (this only occurs in certain places where baboons generalise about humans), drop it. Once the baboon has realised there is no food in your bag, he will leave it and you can retrieve it.
Remember that their motive is to get food not to hurt you! This will help you remain calm and use passive body language as described here.
It is most important to never frighten the babies by looking at them or getting close to them when you come across wild troops while on foot.