Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states: To find a suitable spouse in the west, one may do the following:

1. You may attend various Islamic gatherings at Islamic centers or in mosques and you may engage in business like conversation with the members of the opposite sex, without being isolated with them.
2. You may also make use of brothers and sisters who may introduce you to prospective candidates and talk to them under supervision.
3. You may do some kind of correspondence with candidates who have advertised their names in the Islamic magazines.
In the time of the Sahabah (Prophet’s Companions), they used to meet people sometimes in the presence of the Prophet (peace and blessings be upon him), and sometimes in other circumstances. For instance, on a number of occasions women used to come offering themselves as candidates for marriage. Accordingly, some men would accept to get married to them. This shows that the Sahabah were very simple and undemanding about choosing their partners so long as they had the basic religious and character requirements. In this society, generally speaking, we tend to put so many conditions and requirements that are not essentials from an Islamic perspective. In Islam, the basic thing we should consider in marriage is religion and character. All other requirements we can compromise.
the Companions also used to make other people introduce them to possible candidates. They would see each other and occasionally talk with them in order to determine their eligibility for marriage.
In conclusion, you may choose any of the methods in order to find prospective candidates. Once you have chosen some, you may inquire about them from people who are reliable and trustworthy in order to determine their illegibility and integrity. You are allowed to ask about their past in order to find out the essential points reflecting their character. If a person has a bad past and he or she has changed and improved his or her life Islamically after having repented their sins, you are allowed to marry them. In this case you are not allowed to nag them about their past after marriage.