Wearing trousers which are not fitted properly above the legs, ie too short waisted, droopy crotched, baggy or too tight is the biggest mistake I think. Shape wise I think it depends very much what you wear with them, wide legged trousers look far better with a short, neat fitting top, and vice versa for narrow legged - the worst look is wide legged trousers with a loose top in my opinion. I’ve got jeans with all sorts of fanciful names, including slim mom, girlfriend, cropped cigarette, and retro. I draw the line at paperbag, as they make me look two sizes bigger, or balloon, which look ridiculous on me.