Ditto on "intuition"! I just go within during my labors. Nobody taught me that, it's kindof a primal thing.
That said, sometimes it helps to expose yourself to different ideas so that you have those ideas floating around in your head and accessible to you during labor. Some people really like the suggestions in the Bradley Method book adn classes. I didn't find them helpful. I preferred the ideas in the book Birthing From Within. Some people find "relaxation practice" to be very helpful, I do not. It's a very personal thing.
I also read Active Birth before my 2nd son was born, and while it does not really focus on relaxation or pain management, things I picked up from that birth did end up making my birth a very different/positive experience for me, so I'd recommend reading that as well.
I personally do not aim for pain relief or being pain free, I aim for working with my body, whatever sensations it's experiencing. Sometimes pain/discomfort can be helpful in guiding what we do during labor. The key, for me, is not to be afraid of pain or perceive pain as "bad", but to understand how sensations relate to what is happening in my body, and go with it. Definining sensations differently and not using the word "pain" as a blanket word for all labor sensations is also helpful - it's sortof a mental mindset thing.