For me it has been parenting forums like this one and some Yahoo groups I've belonged to, and then the books that the sane-sounding people there recommended. It's funny....the biggest most positive changes that I've been through as a parent came by following up on some parenting styles and advice from people who absolutely infuriated me when I first heard them. They seemed SO out-there and "permissive" or whatever.....but when I followed up on the ideas, read the books, started to put it all together in my head, reflected on what I had been doing, how I had been parented, trying new techniques....things started changing. We are in a whole new direction now.
As for mistakes, I apologize to my 8 y.o. son and I'm very honest with him. For example if I lose my temper or if I'm being bossy and controlling, then later on when it's a quiet time I may go in and say "sorry I was such a bossy monster earlier. When I'm under pressure from work I can forget how to be patient. I need to work on that, huh" (something like that) and I think he appreciates it.
And we never "go to bed mad." Even when we're grumpy because perhaps he's been resisting bedtime and it's late and we're all cranky, HE will now say "Come back! Hugs! Let's not end on a bad note." And we never do. So just being open and honest and remembering that the times when we are most loving to them are the times that they can draw on for strength later on in life. If they feel like they are 100% supported, even if we feel like we are just bumbling along, then the love & support part will be what they remember, not the mistakes.
Best of luck. And seriously, be encouraged. When my guy was 3 and 4 years old, I think I was doing so many things wrong and we were in conflict most of the time. But after heeding some good advice, things are so , so , so much better. The better I parent, the better HE is!! haha. But I'm a work-in-progress for sure.
Some good books are Unconditional Parenting (Alfie Kohn), Between Parent and Child (and other books by Haim Ginott), P.E.T. (Parent Effectiveness Training) by Gordon, I think it is. Also anything by John Holt. And a web site called Hand In Hand Parenting (read the archived articles), and the one about Non-Violent Communication. I hope those resources help you.