In the words of former first lady Nancy Reagan; "Just say no!"
Unless one is raped sex is a choice! If someone really does not want to be "tempted" then naturally they would seek to avoid putting themselves in a position to be tempted. For example only have group dates, avoid frequent or pro-longed kissing sessions, avoid drinking alcohol or using drugs, and try avoid being alone together in a room. Some people masturbate prior to going out on a date.
Having said that the best way to avoid having sex is to date someone who shares (your) same values!
It's always a challenge to be with others who are not in agreement with your beliefs. One or the other usually caves into temptation.