It's not a rule, I just don't think it looks good. Excessively tall guys already have pretty abnormal proportions, it's probably best to avoid exaggerating that even more. Those particular jeans aren't tapered too much (it was a general comment), but you're mankle rolling them which has the same effect. Basically, due to very long legs and big feet, we want to avoid narrowing the area over the shoes too much because it makes the shoes look even larger and it makes the waist to bottom of leg proportions look even weirder. I don't know if it's due to cropping or you standing too close to the camera, but that picture is badly framed. You've chopped off a bit of your head, which looks really weird. Your shooting height is way too low, looks almost knee height from that picture. Walking towards the camera doesn't help if you're still stiffening up so much that you look like a malfunctioning robot. For quick learning I guess it's easiest to just look at what other people are doing. Look at how Phat Guido and aeglus takes their photos for example.