I sleep best in 1st - possibly due to the bubbles and comfy mattress, In business I also dose on a little wine but reading a solidly boring magazine helps. I haven't flown in economy on long haul since 2002 but, IIRC, I rarely slept well no matter what I did. In those cases I made sure I got a decent kip before flying and treated the flight time as an extended day then crash at the other end.