It really doesn't even help that the resources for self-typing SUCK.
Your first option is to take a standard MBTI test (mypersonality is a good one, IMO) and verify the type with a description. Problem is, while the test might have been fairly accurate, the descriptions are rife with generalizations, leaving the person confused because they cannot relate completely and wholly with it.
So then you decide to upgrade to the cognitive functions test. In theory, this should be a great system because MBTI is about functions and not generic descriptions. But the test itself is something that I found quite confusing (not to mention that I had codified some of the values that the test expected as Fe into my Fi). So you end up with some garble of abbreviations and percentages and go to the web to decode them.
And after a poorly directed google search, you find a extremely abbreviated article on Jung's cognitive functions. What happens is these sites try to compress what took Thomson's Personality Type a good 20 pages per function into a single page.
So don't be that hard on them...