When shopping for new jeans, what is most important to check for quality?

I always do the stretch test to make sure they stretch enough but not enough to where they will fall down. I look for about a 2-3% spandex to denim combination. The other quality is thickness of the denim. There are some jeans out there that are so cheaply made you can almost see through them. When you rub them in your hands they almost have a paper feel to them. Avoid these jeans! They will rip within months of washing and wearing.
I also love name brands. It's unfortunate but I feel like you get what you pay for. However, I am not opposed to sale items or even used items so that is how I save money on designer items.
Levi's are the best all around but you have to love True Religions and Mankinds!