The simplest answer for chastity is no sex outside of marriage. It is that simple. Yet how many choose not to obtain this virtue? Sex and all related forms outside of marriage is a grave sin.
"When you decide to lead a clean life, chastity will not be a burden on you: it will be a crown of triumph." - St Josemaria Escriva
"Only the chaste man and the chaste woman are capable of true love." - St. John Paul II
"Either we must speak as we dress, or dress as we speak. Why do we profess one thing and display another? The tongue talks of chastity, but the whole body reveals impurity." - Saint Jerome
"Chastity is impossible without the Eucharist." - St. Philip Neri
"Just as a tower defends a fortress, so humility of heart defends bodily chastity from the darts of fornication." - St Anthony of Padua
"A man who governs his passion is master of the world. We must either command them or be enslaved by them. It is better to be a hammer than an anvil." - St Dominic