When I take the tests, I struggle with what perspective to take. Do I take the test based on what others would say about me? Is it feeling based? Do I analyze the question? I feel like I'm a good balance of both sides of each coin.
Haha. I answer them based on how I perceive myself, in a most objective manner that I can, using others perspectives as a guiding post at the most. I go on the basis of what I naturally am without the age factor, life experiences etc. If the question doesn't apply to me, or I'm 50/50 I try and answer based on what the principle is behind of what they're asking. Some people can never do these tests and never get a result that reflects them. I have a few friends like this. Funnily enough, my INTJ friends! Some people find it easier if someone close to them, who knows them well, does the test with them. There is professions MBTI testers, but that costs money. If there's someone you know who's clued in, they could likely identify what personality type you may be. Knowing one's 'type' (I do hate that term, as it implies categories) can be helpful, but I don't think it's essential.
Sometimes people find temperament tests a little easier, as they're more generic, and based on that one can speculate as to one's MBTI. The one's that give you a pair - a primary and secondary temperament, are the better ones. (i.e.
http://www.keirsey.com/sorter/register.aspx)
At the end of the day, your a unique individual, that despite having a particular personality, is not limited, defined or restricted by it.