How do you test success?

Here's my two cents on body numbers...
I am not going to say Body Mass Index (BMI) is a useless number. However, BMI is nothing more than a height and weight ratio type calculation. It doesn't take into consideration the body fat percentage or muscle mass.  For  example, if you are short and lean, with a considerable amount of muscle, your BMI will show you're obese.  Likewise, if you are really tall, with little muscle mass, and a beer belly, your BMI might be 'ideal'.
Now, with that being said I believe the BMI has it's place,,, like in the Dr's office.  When a physician notices their patient is overweight, he or she can then figure their BMI to give them a number that tells them they are overweight!  A higher BMI can put you at risk for obesity related health issues.  If a Dr. is trying to help a patient to be proactive and lose weight for health reasons, the BMI number would be very helpful to monitor their progress. 
AGAIN the BMI is just a height to weight ratio.  If you'd like to figure it go right ahead, it's not a bad thing to know.
 Here's the formula for BMI:
English Units: BMI = Weight (lb) / (Height (in) x Height (in)) x 703


Now, here's what's interesting... and proves my above point! Check this chart out!

  The CDC provides the following ranges for BMI values for adults:

Underweight Less than 18.5
Recommended 18.6 to 24.9
Overweight 25.0 to 29.9
Obese 30 or greater

My BMI is 25,,, yes, I am overweight!  Now, don't you think if that were true my Mr. Fitness husband would have me on a strict celery only diet!?!? 
I believe the mirror, and a skinfold caliper body fat test are the way to go!  Now, let me caution you that the body fat calipers can have a huge margin for error!  Now I said CAN, because you really just need to go to someone who does this A LOT and knows what he's doing!  I would also have them take several different measurements,,, 5-8 places on your body and each spot twice... or a third time if there are discrepencies. 

Currently my body fat % with calipers is 16%.
So check out this chart!

The American Council on Exercise provides the following ranges for body-fat percentage:
Essential fat
woman 10-12%
men      2-4%

Athletes
woman 14-20%
men      6-13%

Fitness
woman 21-24%
men     14-17%

Acceptable
woman  25-31%
men      18-25%

Obese
woman 32% +
men     26% +
(These facts/charts come from a trusted source, webmd.com)

So, am I overweight or athletic???  Good question.  I feel like I'm right where I want to be.  I don't want to be any lower body fat% wise because last summer when I was 12% I lost my period for three months!   Okay enough said, I think Body Fat % is more accurate than BMI.
However, there is another measurement of body fat that I have experienced. It is with the x-ray body composition scan machine at my Dr's office.  This scan, like the BMI, is probably used more by Dr's.  They can find out if their patients are carrying too much fat around their organs; which is a huge health risk.  This scan puts my number about 4% higher than calipers (it shows the fat on the inside of your body too).   I  like this scan because it gives you the lean mass amount in grams per limb!  This is a great way to see your muscle growth and of course fat loss too!   The progress from one scan to the next is very noticeable with numbers: body fat %,  grams of lean mass and grams of fat mass!  I would have to say this scan is pretty accurate.  The downfall is the price.  It is ranges from $30-$50 per scan! 
While we are on the topic of money, the upside to the caliper is most gyms will do it for free if you are have a membership, or they usually only charge $5-$15.  
The cheapest way to see if you are making progress in reducing fat is the mirror! 
However, do not rely on the scale to determine your success.  My personal example demonstrates this!  This winter I lifted hard and ate to gain muscle.   All winter and this spring I gained 7 pounds but went down from 20% body fat to 16%.  So, if you know you are working out hard and eating clean don't worry about the scale!   Go get your body fat% done and you will know where you are "really" at!!!