If you don't know about Summer/Winter School Uniform changes then you clearly need to watch more slice of life/cute girls doing cute things shows. I probably learned most of what I know about Japan from Azumanga Daioh (which is why I probably know almost nothing about Japan).
With regard to Death Note, I remember trying a few episodes and being disappointed that Light didn't quite have the personality I hoped. I was kind of hoping he'd try to use the Death Note to help push the world into a being better place where everyone (who survived) could get along without having to worry about crime or war or whatever and then once he'd succeeded he'd be the last name to be written. Basically, sacrificing himself by being a villain so that others could be innocent. I guess the story is maybe a bit like that but I wasn't entirely sold on it.
Still, I watched Death Note at a bad time when I couldn't watch as much anime anyway so that was part of the reason that I never went back to it. I suppose it's technically the first show I dropped but I forget about it because it was before I was really into anime. I don't usually like to judge things by what they're not rather than by what they are so it's an odd exception that I should maybe give a second chance (although I'm not sure I'd be enthusiastic enough to put the effort in, I'm pretty lazy after all).
