In an article titled “We are the 20%” Alexa Tsoulis-Reay, and Mary Jane Weedman interviewed various service sector workers who rely on tips and found out secrets of the trade:

• Odd things affect tips. Being understaffed, being pregnant, or engaging well with children will boost earnings.
• Baristas will usually have two tip jars. One where the coffee is ordered and another where the coffee is made. The second is for people who are moved to tip after they’re dazzled by the beauty of their concoction.
• In coffee shops sad music usually leads to lower tips.
• When bartenders give free drinks, they actually have to pay for it themselves. They try to invest those free drinks in people who will offer more in tips in the long run.

Read more of the stories, tricks, and tips here.

Source: Grub Street