I don't know about MOST helpful, but I know when I first joined, I hadn't a clue about harnesses/collars. That was all new to me. I had only ever put a collar on a dog in my life.
I had no clue about vaccines and vet care type things. I just was always one of those do what the vet says and not really question. After Jackson's 12 week old vet appt. and a reaction to lepto, I began learning things on this site.
I was clueless about food... only after reading a few bad things about Nutro (and still being convinced it couldn't be THAT bad... after all, my families dogs had always done well on crappy foods
)... so then I began to research and form an entirely different opinion.
If I hadn't found this site (about a week before getting puppy Jackson, if I remember correctly), I probably would be a totally different dog owner!