Series\Series - Season <season number> - Episode <episode number> (<episode title>)
Series\Series - Season <season number> - Episode <episode number>
Series\Series - Episode <episode number>
Without offering a solution, the first two should be easily parsed. The problem will be with the file that has no season. The three absolutely required pieces of info are -
1. Series name
2. Season Number
3. Episode Number
Without those three there is no way to correctly determine what episode the file is.
For clarification, do you actually have the words "Season" and "Episode" in your file name - to give an example following your info -
Terminator The Sarah Connor Chronicles - Season 1 - Episode 6 (Dungeons & Dragons).avi
That's a really long file name. Have you thought of shortening the season/episode part to something like - S01E06