No one has mentioned the biggest determiner of all of how much sleep one will get. How close is the nearest crying baby or children not being supervised by parents? You have no control over these factors so it is best just to go for it and realize that the flight will end sometime.......
I have no problems with babies that cry because, well, they are babies and can't help it. I do have problems with parents who do not supervise or control their children. I had an overnight 11 hour flight seated across from a family (Mom, Dad, 3 kids ages 6 and under) where the children were allowed to scream, yell, throw food, etc all night. I think the Mom would have tried, but the Dad put on his phone and ignored everything. She was just overwhelmed and gave up. I had an entire tray of food dumped into the aisle and over my feet. I realized at that point I could get angry or I could try to give that poor mom some help. I cleaned up the mess and helped the mom who was very worried about her shoes and the food. I only had to deal with those kids and that deadbeat dad for 11 hours. She had them for the long haul.
Were they one of the most annoying groups I have ever traveled next to? Yes! Did I wish I was seated elsewhere? Yes! Did I survive and go on to have a great trip? Yes!
So, do all the tricks you can think of, but hope that you are seated near people that will allow you to sleep.