Though it may not be true for the younger people who are part of the dating world, there are some dating singles that wont always know what they do want in a partner. However, the longer you date and the older you get you will probably be very certain and will have (at the least) a mental list of what you dont want to deal with in a person you are dating.
The dont want lists are dangerous in that you may say you dont want to date a guy with a beard or a woman with green eyes. First you are limiting your choices on seriously unimportant aspects of a person as a whole being. And you cant hold a conviction based on outward appearances, simply because you are bound to meet a wonderful man with a beard, or a charming woman with emerald eyes and you become flaky with yourself.
Just like boundaries you set with any person in your life, the boundaries you set for your self have to be consistently enforced. Allowing indecisiveness in your choices of date material will often lead you directly toward the path where you are bound to repeat past mistakes. Since it is imperative you stick to the boundaries you have set its a great decision to allow your dont want list to...