Oh! Well, to be a Connoisseur in general does require an extensive knowledge on the subject--as being a Pokemon Connoisseur in particular is considered more of a profession rather than just a hobby, though, it's very important to do your best! There's more to it than just knowing a lot about Pokemon; there are some tastes you have to experience yourself! It's not just something you learn from a manual, you have to put your heart and soul into it too! [sparkle sparkle]

In Unova, if you wish to become a Pokemon Connoisseur, you take a test. If you pass, you'll become a certified "C-class" Pokemon Connoisseur, and the harder you work at it, the more you can rise through the ranks. "S-class" is considered the highest rank and the hardest to obtain, with "A-class" being the second-highest and "B-class" being the next rank you obtain after C-class...also, when you first start out, C and B-class are usually only allowed to initially be hired as assistants to someone that is of the A-class or higher, where as A-class and S-class are allowed to work independently and can even open their own shops to work from.

[TL;DR Basically becoming a Pokemon Connoisseur is sort of like earning a degree in college or joining a guild. You start out at the lowest rank and then study and work your way up to the top. And it's a job people actually get hired for, though there are those who choose to do it for free like Cilan here.]