You can get a lot of practical TV writing advice from Ken Levine's Blog, but in small doses among other stuff about his past as a writer/producer on "M*A*S*H", "Cheers" and "Frasier" (basically the sitcom gold standard - he even wrote one first season episode for "The Simpsons"), and his other careers: as a movie screenwriter (2 produced, no hits), author of humorous non-fiction books, major league baseball play-by-play announcer, sportstalkradio host and disc jockey (his first career - I briefly crossed paths with him when he was playing off his 'too-high-for-top-40' voice by using the nom-de-jock of Beaver Cleaver... he doesn't remember me, but I was majorly impressed with him) and NOT the creator of BioShock (different guy, same name).

Anyway, he doesn't tell everything online; he has a little side business now of small group courses on TV writing called "The Sitcom Room". Unique experience, exclusive and expensive and only once or twice a year (but you now have a small advantage because of the link above).

But based on what Ken Levine has blogged, you can still try submitting the spec script to the show it's written for, but if they love it, they'll just buy the 'story' and "sitcom room" it into something not totally different. Also, if they really love it and you, they may ask you to wait until staffing time for next season and a shot at a full-time job because TV is mostly 'staff written' (and even more than during Levine's Golden Age), and that's the break most people with spec scripts are really going for.