How to become proficient at password cracking?

[pumba]

It all starts with knowing what kind of passes do you attack, does they have some kind of passwordpolicy (minimum lenght etc.) where are the hashes from? what language was used? most dictionarys are targeting at english passes, you will have some hits on other languages too, but you will never be so succesfull when targeting for example german passes

always look at already cracked passes from that source, this way you can sometimes see a pattern like mentioned above, had a databreach where the passes where ALL of lenght 8, yeah nice to know

Is there some theory that I have to know except what you've said? My impression is password cracking skill is due to 90% of time practicing by cracking hashes themselves and making guesses on password structure, and 10% is some theory