Assuming a late night (23:00 LT)departure, don't sleep on the flight until around 05:00 origin time. Gives you about 4 hours or so before they start shaking you awake for brekkie.
Then go and have a session of foot reflexology to rid yourself of swollen feet, a Japanese meal (cleanses the palate and is easily digestible) and LOTS of fluids.
I use beer.
Then off to beddies-byes at around 11 pm destination time and you'll sleep until 6 or 7.
Works wonders on FRA-SIN.
I made the mistake of sleeping from the off on one of my first flights - you're as bright as a button at 03:00 SIN time and then you die a death as from about 11:00.
Right in the middle of a presentation.
Not good.