Before explaining my point, I think that it is important to state something about the nature of the functions. I believe that each function has specific subsets of traits that seem similar but are somewhat distinct. For example, I can think of two different manifestations of Ne: 1) seeing potential in things and 2) brainstorming; generating ideas for their own sake. These are really two separate (although often related) traits; not everyone who enjoys brainstorming is constantly on the lookout for opportunities, and vice versa.
This is important, because it explains one of the problems that can occur in identifying your type. When looking at the functions that they do not strongly possess, people often oversimplify them. For instance, if Fe isn't in your ego, Fe is often easy to spot in others; such people are sociable, and/or very emotionally expressive, etc. In fact, I find it very easy to spot Fe in other people. On the other hand, I can almost never spot Ne or Ti. Further, I don't see any underlying pattern in a lot of Ne or Ti descriptions. I would argue that the reason for this is that when you use a function, you're going to apply it in a very specific way. For example, if someone applies Ti to mathematics, and another applies it to philosophy, the way they are used is going to seem different. The first person is going to use it to solve problems, the second to perhaps construct and evaluate arguments. Therefore, when reading a description about Ti, if it says that one who uses Ti is skilled in constructing and evaluating arguments, the first person will often not identify with it. To someone from the outside, these skills seem essentially the same, but when you use a function all the time, you tend to identify with the specialized way that you use it, so it might not seem the same at all.
The question is, if this problem exists, how can you type yourself correctly? The answer is that you look at the skills of the function being presented, and ask yourself, "Would I want to do that? Am I capable of doing that well?" It seems to me that people of the same type may behave differently, but most would have the desire and capability of engaging in the different manifestations of the functions of their type in a competent way. The solution from the perspective of the writer of a type description is to be as general as possible. That way, more people will identify with it.