The 28 day rule, if TiVo has already recorded an episode of a show within the last 28 days then it will not record it again unless you set the SP/ARWL to record all episodes or if the show only has generic guide data like South Park the past few weeks.

You should also know this: If you setup an ARWL for "The Wire" set to record FRO you have 14 days from the Original airdate to get the episode. This is nice because if you know of shows that are Shared-Window/Repurposed Network Television if can help you with conflicts.

SP = Season Pass
ARWL = Auto Recording WishList
FRO = First Run Only