There's no need for a full-on shoulder massage, but putting a hand on their arm might help.
In 2004, psychologist Nicolas Gueguen had 20-year-old men approach women pedestrians in a French city and ask for their phone number. Half the time, the men simply made the request; half the time they lightly touched the woman's forearm for one second while asking.
Sure enough, the men were more successful in getting the woman's digits when they'd touched her arm.
University of New Mexico evolutionary psychologist Steven W. Gangestad told Psychology Today that flirting is a "negotiation process" that happens after the first moments of attraction.
It's a subtle sort of testing the waters. You don't just say I'm attracted to you; are you attracted to me?
"It works much better to reveal [your attraction] and have it revealed to you in smaller doses,"Gangestad says. "The flirting then becomes something that enhances the attraction."