Body fat percentages - how to?

Could someone explain body fat percentage and how to properly measure it?  I know there are some scales that claim to measure based on body electrical conductivity, but apparently they are really not accurate.  How do you get this measured on a regular basis?  Now that I'm on the second half of my weight loss journey, I'm thinking this might be a good and encouraging measure for me, but i'm really clueless about it.  And also how does loose skin factor into the measurements?

The online calculators are total garbage. A complete stab in the dark. At least bio-impedence will get you in the ball park.

There is this a great series of articles out there that explains all the different methods and how accurate they are and aren't. It's long but it's well worth reading as it really explains the whole process -- why we can't really measure body fat, we're just guessing even with the best of the measurements, how some are better than others and why, etc., etc.

http://weightology.net/weightologyweekly/?page_id=146

And if you don't have time for the full series, this article sums up the different methods pretty well and is a good start:

http://www.medicinenet.com/script/main/art.asp?articlekey=56 83