I have completely given up on weighing myself because the scale is way too misleading when you are lifting.
Anyways, the proper place to measure your waist is at the narrowest part; usually a few inches above the belly-button.
It's also good to measure your lower abdomen, where your pants sit. To measure your hips, place the tape measure around the fullest part of your lower body, around your bum, almost. I think it's good to measure your thighs, too - around the fullest part at the top.
Don't measure more than once a week because our bodies change so often that the measurements would be inconsistent. Also, measure first thing in the morning, before eating and after peeing.
oh, and don't forget about the extra bloating right before your period - don't let that through you off.