If you're confused about your type, here are some guidelines to help you decide. I think it's probably best to look at the combo of information processing and judging, since these together may be more informative than preference alone.
Here are the terms given by the MBTI Manual to describe each coupling:
NF:The Enthusiastic and Insightful Types
NT: The Logical and Ingenious Types
SF: The Sympathetic and Friendly Types
ST: The Practical and Matter-of-fact Types
I'm going to discuss the NT and NF types then come back later for the ST and SF types. I can't promise it will be my next post, but rest assured, it will be in the foreseeable future.
I. The NF Types
NFs tend to place their focus on "possibilities for people." I think this means everything from being a novelist with the goal of connecting with others through writing (motive is important here) to being a therapist or a teacher. There is a strong orientation towards communication, as well as an attraction to theories of human or social behavior. Usually, the connection to these things is more interpersonal and values-based than logical. Logic may be employed, but it never dictates what the NF holds to be important. The MBTI manual describes these types as "attracted to new projects, things that have never happened but might be made to happen, or truths that have not yet come to light." Truth here is multi-faceted and inclusive of different viewpoints as opposed to being categorical. It tends to be more tied to meaning and subjectivity.
II. The NT Types
The NT types share the NF's focus on possibilities and patterns, but here the beauty of the thing comes not through subjective meaning but rather through the extent to which the thing follows the rules of logic, and exemplifies a clearly defined and objective truth. Information and ideas are evaluated from a detached, impersonal perspective and it is their seeming cogency that matters. An idea that is incoherent simply isn't worth talking about or investing time in, no matter how much potential for meaning it may have. For this reason, NTs may at times seem to restrict the scope of inquiry more than NFs. The perspective is that it is better to limit what may be explored and maintain coherence than it is to embrace the inscrutable and never be certain about one's understanding.