Here's a book I've mentioned before. The questions method helps make it clearer to you what you are looking for and whether the other person is indeed the kind of person that could make a great relationship that much more likely.

Are You Among the 17%
It is estimated that 83% of failed relationships could be prevented if couples asked each other the right questions. For a list of the 1,000 most important questions to ask, click here for Questions Couples Should Ask Each Other.