In many ways they will be hard to spot, unless you have all your defenses up and do not allow the drinks get to your head.  Normally they sit from two to four or five to a table, and what you think are drinks, it is mosstly tea what they are drinking.  They are quite sociable, and if you approach them most probably agree to sit with you.  Since they do get a base salary, and a percentage of the drinks bought when she is with another fellow, she will induce you to drink as much as you can stand.  In many ocassions that is all they will be willing to do, but some may negotiate for further "adventures" for the proper fee.

Unless you have access to unlimited funds, I will advise to stay away from them.  You can spot them by their continuous insistance of ordering new drinks, and by the fact that if you say no, they will get up and leave you.

Normally they are a little older, sit alone and play with the're phones all night.
They are paid around RMB200 a night.

I know a girl who used to work at a bar and her job was to get guys to drink more.

She would go around and drink with people...flirt a little and get them to spend more.

This is all she did, and did not do anything "extra".

She earned around 3k a month but rarely got days off and had to live above the bar with the other workers.  She would get a base pay plus commission on drinks  her "guests" would consume.

She hated the job and moved back to her hometown.

They will be the one's most scadely dressed, younger and over friendly. Watch out for the Russian girls, beautiful but most are fillers

Usually a bit more attractive than the other women (by wearing heavier make-up), sit at the bar by themselves, wear more revealing clothing, constantly looking at phone to check weibo, qq, or the time to see when their shift ends. In Chinese they're called  小蜜蜂 xiao mi feng, or little honey bees. Pay depends on the bar/club. Some pull in quite a bit I reckon.