Assuming that their services are equally good, will you give more tips to a waiter that
stand next to you while taking your order
squat next to you while taking your order
lower his body i.e. bending down, while taking your order
Believe it or not one study found that food servers who squatted down next to their customers to take drink orders got higher tips than servers who stood next to their customers (Lynn & Mynier, 1993)
Supposedly, the increased eye contact and closeness generated more positive feelings. Nobody likes to be 'look down' by others especially if you are a customer.
Lynn, M., & Mynier, K. (1993) Effects of server posture on restaurant tipping. Journal of Applied Social Psychology, 23, 678-685.