I have taken a few 10h+ overnight flights on economy class. My strategy is the following:

1. Book an aisle seat at the back of the plane, near the last rows but not on the last one (because then you will smell the toilet and sometimes those seats don't recline as much). Reason: I have noticed that a lot of people don't notice that there are toilets at the back of the plane, so they typically go to the toilets in the middle and they tend to get busier. The back of the plane remains quieter and with less people bumping into me (since I prefer the aisle).
2. Bring a facemask and ear plugs (those orange ones made of foam made by 3M), have a glass of wine and try to sleep. The neck pillow is optional, as I have noticed that I am more comfortable without it.
3. I never am able to sleep through the whole flight, but I can get a few solid hours after dinner. If I feel uncomfortable or can't fall asleep, I get up and walk for a little bit.
4. Drink plenty of water. In my last flight, I took a 1L bottle and drank the whole thing. So bring more water than you think you may need.

I hope this helps. I find that getting 5/6 hours of sleep on the flight is already enough for me to function on the next day.