Greetings in Chinese culture are quite a bit different than western culture. There are some key differences that are worth noting.
Chinese people generally greet each other by title and last name. For instance, "Hello Teacher Wu" or "How are you Dr. Wong?" are appropriate salutations. It's rude to call someone by their first name unless you know them very well, perhaps from childhood. To say "Hello John" to your teacher would be considered inappropriate.
In China, strangers keep to themselves for the most part. They do not like to make eye contact or smile at unknown people. Doing so is to show too much familiarity and is considered rude. People tend to keep to themselves for the most part, and make momentary indirect eye contact to people around them.
Introductions to Chinese people are often done with a handshake. Sometimes a polite hello along with a nod or smile is sufficient. Saying "what's up", "how's it going", or similar are only used with friends and close acquaintances. Hugs and kisses are not the norm unless it's amongst good friends or close family. You would not give a hug to your aunt and uncle for instance, but you could hug your mother and father.
Younger people may use family names for their friends or acquaintances. A slightly older friend is often called "big brother" or "big sister", while a considerably older friend is called "uncle" or "aunt". It is a sign of respect and friendship to call them by these names.
References to age in Chinese conversation are shunned upon. It's too easy for age remarks to be misconstrued and the receiver of the comments to become offended. A comment may have been meant as a compliment, but it may be misunderstood or taken out of context, so it's best to not bring age into conversation.
Chinese people have great respect for elders. Younger people are expected to let older people speak first, sit down after the older person, and generally not disagree with them. It's not uncommon for an entire room to stand when an older person enters. Using two hands to pass an object to elders is a common courtesy, as is giving up your seat to elders on a bus.
If you will travel to China or are meeting with native Chinese people, it pays to do some research on what's acceptable in their culture. It can help avoid embarrassing situations. Chinese people are however very understanding of the fact that western cultures do not always understand their culture, and are very forgiving of misdeeds.