Well, one of the ways in which I type people is by identifying the 8 functions through whatever data is available.
For instance, Facebook profiles can provide many clues to type. Whenever I friend someone, I want to have as firm an idea as possible to who they really are, and I look though the profile pictures of a new friend to figure things out. bear in mind that type does not necessarily translate to FB saviness or usage, the "unique individuals" factor must be applied. What I have noted...
Extroverts put out more pictures. Introverts may update a lot, but extroverts put out more pictures. Furthermore, these extrovert pictures are more extreme in regards to certain elements...
Fe doms - People. Generally, ENFJ's and ESFJ's put up profile pictures in which they are posing with other people. This is done in a manner that shows off their friends and family, kind of like saying "I establish relationships, and these are examples". These pictures appear to be deliberate poses, and the EXFJ has an established picture-smile on their faces.
ENFP's - The Ne (and even SFP's) users are similar, but different in essentials. The presence of other people may occur, but they are not the focus. The focus is on the activity, and the people within the profile pictures are not posing as much as they are caught in the moment doing something. Kind of like "Hey look here, cheese, alright!" The P type smile is more unbounded than the J smiles, and they are also more varied.
As for the introverts...
I've noted in confirmed and suspected INFP's I know that their profile pictures feature the art that they revolve themselves around. For instance, a professional jazz drummer I know has several pics of him at the drums. My designer friend has a few pictures of herself in medieval garb, and artists often upload their art into their profile pictures. Beyond this the INFP will post like other introverts, low frequency and often erratically, and what they do upload will be more reserved than their extroverted counterparts.
The INFJ is tricky. I only know three confirmed INFJ's, and none of them are very facebook oriented. They post pictures erratically and have since become stagnant (no new pictures ). Meh, figures with Ni :rolli:
In application to real life, the way I see NF's
ENFJ - People oriented. Their idealism focuses on people and relationships, family is huge with ENFJ's. I would know, my Mother is one and her main focus is family.
ENFP - Energy focused, namely with activities and what they do with people. They are often alternatively minded. I'm not so sure about this, and I know only one ENFP for certain, and she hasn't even been tested yet. However, she is a Yoga instructor and wants to have a career in Holistic medicine.
INFP - They are reserved to a level, and seem to focus on whatever it is they create, whether it be art, writing, music, or whatever.
INFJ - They too are people oriented, but are more flexible. Hard to find really, good place to start is under rocks
Also, if people are having trouble ID'ing types, then I would suggest moving away from the four letter codes. Those are meant to indicate the order of preferred functions, and are a little limited in scope to determine a full personality, which in and of itself is difficult. Try to ID the 8 functions rather than the j/p. ENFJ is Fe dom, ENFP is Ne dom. These are significantly different and easier to pick up on than trying to see if the person uses schedules or not.
(on a side note my whole facebook thing is a Ti construct that applies to both web and face based communication and is not limited to just facebook)