How to address a person properly depends on a lot factors, but as the rule of thumb, Chinese people like to use 2 characters to address a person.
The reason is that, I guess -
1) using 1 character from the given name sounds intimate (like between lovers),
2) using the person's 1-character surname sound foreign. In English, if a person's surname is Wang, we can address him as Wang, no problem, but it is very weird to address him as 王 in Chinese.
3) if a person's name has 3+ characters, and address him/her using his/her full name sounds too distant.
If a guy is named 王良, it is natural for people not too younger than him to address him by his full name, as his name has 2 characters. A guy a few years younger than him may call him 王哥 to show a little closeness. A young lady may also call him 王哥, but it may sound flirty if she says 王哥 in a certain way.
If a girl is named 张玲, it is natural for people not too younger than her to address her by her full name, as her name has 2 characters. A guy or girl a few years younger than her may call her 王姐 to show a little closeness.
When meeting people for the first time, we can use 先生 to address men, like 王先生, and use 女士 or 太太 (if she is married and likes to be addressed that way) for women, like 张女士, 刘太太. 小姐 was a formal/good way to address ladies, but nowadays it is assigned with another meaning (hooker), so avoiding using 小姐 if you are not confident with maneuvering the subtleness.
In the workplace, people use surname + title to address a person, like 李经理, 张总, 王处长. If your boss addresses you as 李经理, it shows some distance between you two. If the boss addresses you as 老李 or 小李, it shows closeness.
Between close friends or family members, given names can be used to address someone. Givenames have almost always 1 or 2 charaters.
If a person has a 复姓 (99% of all 复姓 have 2 characters) like 上官, 欧阳, 司马, usually people address him/her by their surname.
Even for Chinese natives, sometimes we can't figure out the proper way to address a person either, so we will try the most conservative ones first, like 先生/女士, and usually that person will tell you what he/she prefers to be addressed as.
If your friend is not a Chinese native, then I suggest him picking a 2-character Chinese name directly translated from his original name, like 马克 for Mark, just forget about the surname. So in this way 马克 can be used by EVERYONE, because for directly translated foreign names, the necessity of properness is much less, after all it is already foreign, isn't it?
One note on translating original names into Chinese: you need to make the Chinese name sound foreign, and avoid the names sounding close to the existing Chinese words. For example, if your name is Philip, don't pick 菲力, as it sounds close to 费力, or 非礼. In this case, go with 3-character names, like 菲力普.
