I've spent some time venturing other sites, trying to get a grasp on how we can change up this site a bit. Regarding characters specifically, a few VERY good sites insure that if a character DIES within the season, they don't mention it until later on. So basically, any characters who are alive from the start of Season 1 should be referred to in present tense rather than past-tense. This also means sections should not include in the title "Death" and specifically a spoiler tag should be provided before any section detailing a death.
An example of a character who has been dead since the start of the series and CAN be referred to in past tense: Harry Morgan. This is clear, from within the first 10 minutes of Episode 101: Dexter that Harry Morgan has passed on as Dexter confirms it (jokingly) that both his parents are deceased...and don't worry, "he didn't do it".
I'll use a minor character to prevent spoilers, Mike Donovan. He should be referred to in Present Tense because he is alive at the start of the season though...killed relatively quickly. Regardless, someone who hasn't watched the show yet won't be like "Ah man, I already knew he was going to die!". I'm contemplating removing the Category "Characters killed by Dexter" because of this.
Let me know on my talk page if you are interested in working on all character articles to make them appropriate. If you have question on which character should be present and past, I'm open ears.