I personally got a lot from reading an ebook called The Sex God Method by Dan Rose. Don't know if you can still get it, it was years ago but it really changed my mindset towards sex and improved things a lot for me. However, I think if you've not had sex before probably one of the worst things to do is fill your head with theory and end up over-thinking everything. I suppose sex is a lot like a conversation with a girl - it will be different every time and it's not really something you can rehearse. You just have to go in and enjoy it as much as you can, then reflect on what you could do differently next time.