Before you marry one should offer the Salat al-Istikharah prayer. This prayer is found in most Dua books like Al-Hisn al-Haseen. The istikharah prayer is done to dain Allah's taala guidance on whether the person you are contemplating marrying is right for you; for it is impossible to tell the inner nature of a person and it is folly to decide on outward looks. Similarly, one should offer the Salat al-Hajah (the prayer of need) before you begin the search for a spouse. There is no exact time for these prayers, but they should be performed as early as possible when a possible spouse is found. In the case f both prayers one offers two nafls after which one supplicates to Allah taala using a special dua. In addition to this, it would be beneficial if you buy a book on the subject of the Islamic Marriage by a reputable scholar that will explain in more detail the issues you should be aware of.