If you have not seen The Wire, here are some suggestions:
* Watch it with subtitles, so you can understand the slang of the different subcultures of Baltimore. Otherwise, it's easy to miss many important details. The actors -- many of whom are actual former gang members, police officers, judges, politicians, teachers, etc. from the city Baltimore, speak as the characters would in real life -- not always in easy-to-understand dialects or accents.
* Bookmark the Wikipedia page on The Wire's characters, so you can look them up: https://en.wikipedia.org/wiki/List_of_The_Wire_characters -- there are well over a hundred important characters, and sometimes it's a good idea to pause the show and look a character up to refresh your memory if you don't remember a particular name.
* If you're not naturally interested in Baltimore's police and drug gang subcultures, you may find the first season a bit slow and much of the dialogue full of seemingly unnecessary detail. I would recommend sticking with it through at least the beginning of the second season, which is mainly about longshoremen and unions, before passing judgment. The Wire is not about police, nor about drug gangs. It's about the city of Baltimore.