Casually Touch Them. Subliminal touching is when you touch a person so subtly that they barely notice, but goes a long way. Things like tapping someone’s back, touching their arm, etc. can do a lot for building warmth. In a study conducted in Mississippi, they looked at the results of interpersonal touching and tipping in a restaurant, and found that waitresses that briefly touch a hand or a shoulder when returning change, got greater tips.