With DD1 I did the optimum foetal positioning thing with knobs on. I managed to turn her the "right" way, but then she turned right back again at 39 weeks and stayed that way - she was born "face to pubis" (lovely!). I think that OFP is a good idea to try, but certain women have a pelvic structure that encourages the baby to lie back-to-back (this is from my midwife), so please don't beat yourself up about it if you have a stubborn baby!
I'm trying OFP again this time, by the way, but DD2 is also back-to-back. I have between 5 and 10 weeks to turn her. We'll see.