If you really want to test your bodyfat, hydrostatic is the most accurate. Of course, it is not the most practical. The calipers are good, but there is a 5% variability w/ them. Tanita absolutely sucks! They only work for certain people, and if you have anything to eat or drink, 2 hours prior to, it will scue the results.
If you want to use the calipers, use them simply to check your progress. In other words, get tested in the beginning, then train for about a month, then check it again and compare your results. That is actually what calipers where designed for.