My ex-MIL told me to rub whiskey on my son's gums when he was teething. I know that's an old wives thing, but I couldn't believe anyone this day and age thought it was a good idea. I never did it, of course. She also offered lots of other really weird and outdated advice.
My sister had a rough time with the lactation consultant at the hospital where she gave birth to her first baby last summer. The woman totally demeaned her, told her she was doing everything wrong (she even said that my sister wasn't supposed to be using the boppy while sitting up in bed and had to be in a chair to use it!) and pestered her and made her keep breaking suction and adjusting instead of just letting the new pair figure it out for themselves, which frustrated both mom and baby of course. They were doing fine until she stuck her nose is. My sister almost gave up nursing right then and there because she didn't feel like she'd ever get it "right". I was so pissed, and that lactation consultant is lucky I was 3000 miles away at the time. My mom and I managed to help my sister salvage the situation, but that's an example of way too much of the wrong advice, since we all know nursing moms and babies should work out what feels right for them.
Anyways, there's lot of bad advice out there. Find someone that you consider very successful with their own children and use them to bounce ideas off of. Ignore the rest.