I use Plex to stream my TV and movies to multiple devices around the house. Plex is pretty good at finding show details and cover art, but its always best to keep the files in an organized folder structure. I prefer to keep TV and Movies in different folder and then use a folder structure of that included the show name, season info and title of the episode, for movies I include the year the movie was released.
Do that process manually can be a real pain, but I found a free tool to helpme make the process easy.
Checkout Filebot it will scan multiple online sources to find information about the file and help you rename the file including any folder structure to include the information needed for Plex and XBMC to quickly scan your media.
Check out the video below for an example on how easy it is to use
I don’t use them but filebot can also download subtitle files.