I first got into Barney Miller in my first year of university, when a Canadian cable channel was running the show five times a week. I had no idea they were running it but I flipped onto one of the weaker early episodes once. Eventually I ended up catching better episodes, and after finding more about the show, I starting watching regularly when they were running season 3. Unfortunately the channel didn't keep with the reruns long enough to get through the entire series run, but by the time they dropped the show in the middle of season 7, this sitcom about the mundane work of plainclothes detectives in Greenwich Village cemented itself on my all-time favorites list.
The first three seasons, the ones with Abe Vigoda, are available on DVD. Season one is the weakest and least characteristic, largely because it splits the focus between Barney's home and work life. It became apparent early on that the squadroom was where the show's pulse was, and by the second season the action would rarely leave the confines of the 12th Precinct. Season three is the best of these three: two of the shows, "Werewolf" and "Hash", are considered by many as the greatest episodes of the series. It's also the closest in tone to what it would be for the rest of the series; the shows are considerably more low-key and dry than the earlier ones, which have more of a regular sitcom feel to them.
The other thing that brings season three up to the high standard of the rest of the show is that the characterizations are all firmly in place at this point. The earlier episodes had the characters painted with fairly broad strokes: Barney (Hal Linden) was the normal one, Fish (Vigoda) was tired and incontinent, Wojo (Max Gail) was somewhat dense but well-meaning, Yemana (Jack Soo) was a deadpan joker. It actually took almost two full seasons before the character of Harris (Ron Glass) was fully established; earlier episodes have him acting more hip and urban before he settled into the more satisfying characterization of the upwardly mobile aspiring writer. The ensemble was rounded out by easygoing Puerto Rican cop Chano Amenguale (Gregory Sierra), the focus of one of the stronger early shows, "The Hero", which deals with his guilt after killing a suspect in a hostage situation. Amenguale doesn't last past the second season but by that point the writers were bringing out shades in the other characters to make them more three-dimensional, with the possible exception of chronic reminiscer Inspector Luger (James Gregory).
While Fish was the breakout character on the show early on, I actually think the show got even better after he left thanks to two characters that began to appear semi-regularly on the show in Vigoda's final season: Arthur Dietrich (Steve Landesburg), the precinct intellectual with a deadpan sense of humor that even outdoes Yemana's, and Officer Carl Levitt (Ron Carey), a diminutive and obsequious uniformed cop looking to move up to detective. Production-wise, the show started getting a bit more ambitious. While it started out taped in front of a studio audience, rewrites would be done while the episodes were being shot and a taping session could last late at night; by mid-season 4 the audience was gone and replaced by canned laughter. Usually canned laughter is shorthand for hacky, but this actually coincided with the shift away from the broader tone of the earlier seasons, and was done to good effect. The writers also began doing these long multi-episode character arcs that would play against the regular goings-on, such as Harris' trouble finding an apartment, and Miller's marital issues.
One thing about the show I've always admired was the direction it took in some of the later seasons, with some of the most downbeat material ever done by a sitcom. The season 6 finale, "Fog" has Barney depressed and frustrated after being passed over yet again for a promotion, and despite a comic subplot with the actor who played Cheswick in One Flew Over The Cuckoo's Nest screaming paranoid about satellite dishes poisoning him, the episode as a whole has a gloom to it to match the title. Season 7 opens with a two-parter where the 12th Precinct is reassigned into doing all homicide cases, and a recurring character ends up as one of the victims. The finale ends with Harris weeping on his desk after being forced to liquidate his assets when he loses a libel suit (to keep from straying too far from being a sitcom, though, he does fumble in vain for his gun when the man in the holding cell starts a chorus of "High Hopes). Between those episodes we also got a Nazi war criminal, Agent Orange exposure, a brief jail visit for Captain Miller, and the outing of a uniformed officer (ending an arc started the year before). The next season seems to be a conscious step back into a lighter mood, but thankfully nowhere near "wacky sitcom" territory.
Another thing about the show I've always found interesting was the number of times they would reuse the same character actors in numerous roles over the course of the series. I'm going to dedicate an upcoming post about the ones that strictly appeared as different characters, but there were a few that would appear in different roles a couple of times and then get their own recurring character; this category includes John Dullaghan (eventually playing the lonely transient Ray), Mario Roccuzzo (eventually the one-legged Good Samaritan Mr. Deluca), J.J. Barry (eventually Arthur Duncan, shameless mugger of the handicapped) as well eventual series regulars Steve Landesberg (as a fake priest) and Ron Carey (the titular character in "The Mole"). This practice seems to have fallen out of favor a while ago, thanks to the shift towards increased continuity in series television.
I do hope Sony releases the remaining seasons on DVD, or at least licenses them out to a third party (like Shout! Factory) as they did with The Facts Of Life. The show has been in reruns on cable off and on but usually not as widely available as other, lesser sitcoms of the era. It is worth checking out wherever you can find it.