I grew up with parents flying by the seat of their pants. No real theories or guidance. Timeouts, a few spankings, lots of lectures
By the time I was almost in middle school my dad started listening a lot to Focus on the Family. That was the kind of mindset in the churches we attended, but it was never a focus of sermons and there was no "spank the love of Christ into your children" stuff that I noticed.
My friend had her first before I did and I read Ezzo on her recommendation when visiting her. She also had something from Pearl that she presented as comical but possibly applicable later. It all made so much sense
When I got pregnant I fell in with a hippie dippy crowd and found a better way. My SIL sent me Babywise which I read sometimes early on and felt was just so wrong, but it made me doubt myself a lot too. I stopped reading it. More kellymom, more GCM, more Sears, etc. I found my way much more confidently well before DD was 1 and DH has been on board the whole time.