http://omatsu123-bodybuilding.blogspot.com/2011/09/skinfold-caliper-measurement-for-women.htmlThis has been asked again and again, so here we go!
And use this site to calculate. Scroll down to find instruction for female.
http://www.linear-software.com/online.htmlYou can also use tape measure for body fat calculation at the this site but it's very less accurate.
What are the guidelines for percentage of body fat loss?

Please read the detail at
http://www.acefitness.org/blog/112/what-are-the-guidelines-for-percentage-of-body-fat/How do we look like at what body fat%?
http://www.leighpeele.com/body-fat-pictures-and-percentagesI guess women look best around 18-20%. But as we get older, we need more muscles and less fat, so that our skin is tight enough. So for me, 17-15% is ideal.
My measurement is Tricep 12cm, Suprailiac 10cm, Thigh 17cm.
I am 46 years old now, 52kg(114lbs). 159cm(5.21ft) and 17.92% as of 03sep11