right click on the episode and click 'get info', in the box that pops up click the 'info' tab. on the right side there are track numbers and stuff. you might want to check those numbers and make sure they are all in order. (i.e. out of the same # of tracks, same # of discs etc.)
If you option-I on any file in itunes now, there is a new "sorting tab" so that you can specify the sort order
Now that we're on the sorting subject. Let's say I have 22 or so Office Season 2 Episodes that I may have ripped off of The Office Season 2 DVD and I added them to iTunes. Now I want to make sure the tags for the Show and Season are correct but, I can't change multiple files at once, I have to edit them one at a time. Is there a faster way to do this? It's kinda time consuming if you have a lot of shows to name.
I use a program called Lostify to tag them. It's one at a time, but you can lock the fields so you only put it in once.