In Chinese daily speaking, Chinese people seldom use 'ni hao ma' to greet. Just when you really care about the person's health or living condition, you can use this question to greet. This is a little different from 'how are you doing' in English.
Around meal time such as breakfast, lunch and dinner.People will use 'ni chi le ma?' It literally means have you had your meal. But in fact people don't care if you have eaten some thing, it is used as 'how are you doing' in English.
At other time, people will state what is happening on you.e.g. you are going out of your house and meet your neighbour, he probably say:"ni chuqu ma?"(Are your going out?) to greet. They are not really nosy and you can take it as 'how are you'.
When you come back, your neighbour may greet you by 'ni huilai le '(You are back).
Now you may have a feeling, that when Chinese people express some daily life's affair, they may just greet to you. When they use 'ni haoma'(how are you) that really means they care about you.