For me, hands down, the internet and homebrewtalk as experimentation.
Being the anal engineer I am, I did about 40 hours of research, all on the internet, before I bought anything. Then I dove right in, head first, with all-grain and kegging. I immediately had good beer. Then, constantly reading more and more on the internet, I have continued to improve my beer my varying processes and experimenting with what works best for me (with lots of internet inspiration). With experimentation, I have learned much about the ingredients and hops schedule.
Most recently, I have started adjusting water and pH, thanks again to the internet and homebrewtalk. I will be able to taste the results in two weeks.