I use
Lostify to do this kind of processing, makes it easier to work with batches of files such as whole seasons of TV shows. Basically, whatever you do it seems to take a bit of fiddling around to get TV shows to appear the way you want them to in iTunes because messing up one field on one episode can make that episode appear as if it were a season all its own. Use Lostify, or just select all relevant episodes in iTunes and edit them at once, so that you can be sure that the show name and season number are 100% consistent.
If you do use Lostify, you can lock Lostify's setting for 'TV Show' so that by default everything you run through it will enter iTunes as TV show episodes--that way even if you don't feel like messing around looking up correct titles and production codes that day at least when you go to look for your TV shows they won't be hiding under Movies.