Question about Measuring

Hopefully some of you can help give me advice on this.  I decided to peek a little today, even though it's not time for me to update my measurements.  Some of my measurements seem to have gone down, others seem to have gone up.  Although, I didn't really take too much time - it was just a real-quick "I wonder where I am" measurement session.

Here's my question, though.  What do you do, if you measure yourself, to make sure you measure in the exact same spot every time?  Seems impossible if you ask me, so that means there's no guarantee that your measurements are correct each time.  However, if you can see a definite decrease month after month, then maybe it doesn't matter so much.

I think I know where my waist is.  And my calf, and of course my neck.  My hips, well, there's a tummy to deal with so that's difficult.  My thighs, I can't see very well, but I do use a mirror.  My upper arms, sure, I think I can find the middle.  And my chest - that's not terribly difficult for me to measure.  But the same spot every time?  I'm not so sure about that.

Any thoughts?

Oh, and I measure myself with this (pretty nifty, I think): Myo Tape