Part of the process of determining your type has to do with digging through all of your learned behaviors to see who you really are inside, beyond your own self-image.
The standard model of functions is four of the eight, even though we use all eight functions throughout our lives. The dominant, or the first function, is the one we develop as soon as perception begins. The supportive, or second function, develops as we begin to mature (usually around the pre-teen age). Our tertiary, or third function, begins conscious development in our twenties and thirties, although you may notice that, as you are or were going through teenage years, you began to grasp the concept of your tertiary function. Some of us begin development of it consciously even in teenage years, but that is very uncommon. The last, or inferior function, is developed in the forties and fifties, but may not be developed at all, depending on how well the other functions are employed and what biases are at hand.
That is the natural order of things. Frequently, however, we find that life throws all sorts of hurdles at us that delay natural development and mask it, and even force the unnatural development of some functions. Occasionally, this can be good, such as developing one of the functions to better deal with a living situation, but often times, this unnatural development is bad, and it may impair your true perception of yourself.
Fi, Introverted Feeling: Corresponds to values and beliefs in the inner mind. Those who use Fi may be stubborn in their beliefs and values and may even be easily offended if someone goes against what their beliefs are, even if they do not say anything about it. Although you may think of a man arguing all of the time, those who lead with Fi are INFPs and ISFPs, so they often may not even express their emotions to the fullest extent. Fi corresponds to: Dominant (ISFP, INFP), Supportive (ENFP, ESFP), Tertiary (INTJ, ISTJ), Inferior (ENTJ, ESTJ). If you determine Fi is your dominant or supportive function, you can determine that you are an xxFP.
Fe, Extroverted Feeling: Corresponds to the desire and working for outer harmony. Those who use Fe may be overly focused on everyone getting along - in worse scenarios, they may interpret a small argument as a full-blown battle, even between two other people who aren't interacting with the Fe user. Those who use Fe have a great ability to tell and to care for the well-being of others, though, so you may think of the camp counselor when you think of someone using Fe. Those using Fe are more likely to press down their own needs for the sakes' of others in the beginning, but may be prone to complaining behind their backs. Fe corresponds to: Dominant (ENFJ, ESFJ), Supportive (INFJ, ISFJ), Tertiary (ENTP, ESTP), Inferior (INTP, ISTP). If you determine Fe is your dominant or supportive function, you can determine that you are an xxFJ.
Ti, Introverted Thinking: Ti focuses on specifying, analyzing, and defining within the inner world. Those who use Ti have an inner system in which they categorize everything, and these categories may be very specific. The Ti mind is a very natural analyst. Those who use Ti seek clarity, and may, at times, come across as too complicated to others, even if this is not the case. Ti corresponds to: Dominant (INTP, ISTP), Supportive (ENTP, ESTP), Tertiary (INFJ, ISFJ), Inferior (ENFJ, ESFJ). If you determine that Ti is your dominant or supportive function, you can determine that you are a xxTP.
Te, Extroverted Thinking: Te focuses upon organization and efficiency within the outer world. Those who use Te have a drive to make things as efficient as possible, whether to solve problems, manage things, or even to carry out their future plans. Those who use Te seek results over clarity, and may press for work to be done and decisions to be made even if they do not have enough proper information. Those using Te become impatient when no results are made, but are easily pleased when they see objective progress. In striving for efficiency, however, Te may be prone to neglect personal feelings, whether their own or the feelings of others in the process. Te corresponds to: Dominant (ENTJ, ESTJ), Supportive (INTJ, ISTJ), Tertiary (ENFP, ESFP), Inferior (INFP, ISFP). If you determine Te is your dominant or supportive function, you can determine that you are a xxTJ.
Those are the major judging functions. The T and F scales represent how we make decisions, as you may know. The way the functions are set up are that we have one N function, one S function, one T function, and one F function. The N and S functions serve as our perceiving functions, and we prefer one as the major perceiving function, and the other as a minor perceiving function. The same is for the T and the F functions: we each have a major judging function, and a minor judging function within the model. My major judging function as an INTJ, for example, is Te, and my major perceiving function is Ni. My perceiving function leads, however, so my judging function serves to make the 'whims' of the perceiving function possible, much like the perceiving function of someone who has a T or F function as their dominant would serve the judging function.
Extroverted Sensing, Se: Se is often misconstrued as the function that always needs excitement, always involved in some zany activity or another. This is not usually the case, but can be in more extreme situations. Se, as a perceiving function, perceives the present 'as is', and can actually be energized by taking in information that way. Se also seeks stimulation to keep perceiving, which may lead those using Se to involve themselves in risky or at least odd activities. With Ti as a partner, Se may seek stimulation through such objective experiences (or anything interesting), or with Fi as a partner, may seek stimulation through connections with others. Se corresponds with: Dominant (ESTP, ESFP), Supportive (ISFP, ISTP), Tertiary (ENTJ, ENFJ), and Inferior (INTJ, INFJ). If you determine Se is your dominant or supportive function, you can determine that you are an xSxP.
Introverted Sensing, Si: Si is, at its basics, associated with past memory and recollection. Si does not actually correspond to memory, however. Si perceives information in the present through a 'lens', one of that of the past. What that means is that Si is always situated in the past, and uses those experiences to perceive and draw information from what is going on in the present. This can give those who use Si a 'worn' feel to others, in that they seem to focus too much on the past instead of what's going on right now. That is how Si naturally functions, however, so it ought not be discouraged. Si corresponds with: Dominant (ISTJ, ISFJ), Supportive (ESFJ, ESTJ), Tertiary (INTP, INFP), and Inferior (ENTP, ENFP). If you determine Si is your dominant or supportive function, then you can determine that you are an xSxJ.
Extroverted Intuition, Ne: Ne is a connector - when perceiving information, those using Ne are capable of constant connection from one item to the next, making them capable of creating and employing unique solutions in dealing with the world. Ne is a very present-oriented function, using the present as a lens for viewing the future. Those who use Ne may be viewed as 'hyper-active' or 'random', and may even trip up others in conversation, including fellow Ne users who may not follow their exact chain of thought. One classic example of how Ne perceives and connections information is the letter example. Assuming A is the beginning and Z is the conclusion to something, Ne follows a trail not unlike this: A-C-L-S-U-Z. As such, Ne users may be perceived as jumping around from wall to wall with nothing to anchor them. Ne corresponds with: Dominant (ENFP, ENTP), Supportive (INTP, INFP), Tertiary (ESTJ, ESFJ), and Inferior (ISFJ, ISTJ). If you determine Ne is your dominant or supportive function, you can then determine that you are an xNxP.
Introverted Intuition, Ni: Ni perceives information and looks for patterns in the outer world, relating the perceived info to the inner world. Much like Ne, Ni has an eye for the future, but in the reverse sense of how Ne functions: Ni uses the future as a means of looking at and perceiving the present. Ni is a very unconscious function, and as such, those who use Ni may be perceived as relying on their 'gut feeling' too much, as they often have a hard time explaining how they arrived to a certain conclusion. One classic example of how Ni perceives information is the letter example. Assuming A is the beginning and Z is the conclusion to something, Ni follows a trail like this: A-C-L-S... Z! Instead of the conscious connections that Ne makes, Ni is more of a quiet analyzer, coming to a sudden conclusion all at once, skipping ahead as the pieces all fall into place. This can be thought of as an 'ah-ha!' moment, but not quite so dramatic. Ni corresponds with: Dominant (INTJ, INFJ), Supportive (ENFJ, ENTJ), Tertiary (ISFP, ISTP), and Inferior (ESTP, ESFP). If you determine Ni is your dominant or supportive function, you can then determine that you are an xNxJ.