Linguists call Chinese a tonal language. Getting tones right is pretty tricky for English speakers learning Chinese, but it's important. In Chinese, people's names are written surname first , and given name last. Chinese leader Jiang Zemin is Mr. Jiang, not Mr. Zemin. Sometimes Chinese people give their names in reverse order in English.
Most Chinese surnames consist of a single Chinese character, but a few have two.
There are only a few hundred surnames in use, so lots of people have the same last name. See the Surnames page of Animated Chinese Characters for a list of common Chinese surnames. Most Chinese given names consist of one or two Chinese characters. Parents sometimes pick very unusual or creative names for children, rather than relying on a more or less standard set of common first names as in English. The only way to be sure is to ask them.