According to Quran and Sunnah|
The Noble Qur'an - Al-Ma'idah (5) : 5
"....(Lawful to you in marriage) are chaste women from the believers and chaste women from those who were given the Scripture (Jews and Christians) before your time, when you have given their due Mahr (bridal-money given by the husband to his wife at the time of marriage), desiring chastity (i.e. taking them in legal wedlock) not committing illegal sexual intercourse, nor taking them as girlfriends...."
Cohabitation with a Servant
Hadith - Sahih Muslim, Narrated Abud Darda'
Abud Darda' related from the Prophet of Allah that he came upon a (slave) woman who was in the advanced stage of pregnancy at the door of a tent. He said: Perhaps he (the man accompanying her) intends to cohabit with her. They said: Yes. Thereupon Allah's Messenger said: I had decided to curse him with such a curse as may go along with him to his grave. How can he own him (the child to be born) and that is not lawful for him, and how can be take him as a servant for that is not lawful for him?
A Muslim CANNOT date because Islam protects us from ourselves by segregating men from women who are not directly related (these people are known as mahram) as specific in the Qur'an. Instead of dating, a Muslim and Muslimah meet in a pre-arranged place (such as a room in the Masjid) with a wali/witness/guardian/escort present in the room. The couple will discuss a marriage contract and ask questions of importance to them regarding marriage. The best person to seek for a spouse is the pious.