The first time I ever went down on a girl (sophomore year of high school, I think?) And girls need to feel relaxed in order to enjoy oral SEX. How to go down on a girl in a way she'll thank you for. to go down on her for several hours – just a few minutes of oral sex can do wonders for. So let's address it: how to give a girl oral sex. Begin to kiss and lick her inner thighs in addition to running your hands up and down her legs, drawing closer.