My flying has mostly been restricted to cattle class and I can offer the following advice to those in a similar position.

  • If sleep is a priority, take the window seat. You will not be disturbed by other passengers wanting to stretch their legs or go to the toilet.
  • Take or find a cushion to sit on that lifts the base of your spine off the seat. It's rather the opposite of lumbar support but the design of air seats means I always get sore around the top of my backside/coccyx otherwise.
  • Invest in a neck pillow. I find those with a flat neck are most comfortable.
  • Invest in some noise cancelling headphone. You can use many of the active types even without listening to music ; if you can't sleep, they greatly improve the experience of watching the movies too. Otherwise ear plugs.
  • Take off your shoes
  • Wrap yourself in the blanket but make sure the seatbelt is on the outside of the blanket, with the buckle visible. The cabin crew will then leave you alone
  • Wait until after take off is complete and the plane has leveled off. Because of the pressure drop, most people doze off during take off but you are very likely to be woken soon after (for drinks or people moving around when the fasten seat belt sign goes off) and I find it hard to get back to sleep again. I wait for the drinks and therefore ensure I am sufficiently hydrated before my kip
  • Go to the toilet before you sleep so you don't wake up busting
  • I am short and therefore can adopt a couple of different positions for sleep. for me, the most effective is as follows: I fold down the table as if to eat ; I arrange the neck pillow on the table with one half for my face/side of head and one half to protect the top of my head from the seat back of the seat in front ; I cross my arms and drop them into my lap under the table. The position is not dissimilar to the ''brace'' position but, of course, I am using the table for support.
  • Another two you might try (but the cabin crews don't often like it) are: to fill the seat well between your seat and the seat in front with bags, soft stuff on top; push your seat back as far back as possible ; your backside (and weight, sitting) on the front of the seat, legs crossed on top of the seat-well stuff ; some soft support placed behind your on the seat  ; neck pillow round neck, lean back... or... (this is hard to get away with nowadays)...
  • ...if it's a long flight where the cabin crew slip off to hide and rest when the lights go down, go to the back of the section of the plane you are in (or another one if you are bold) and check if there is a gap between the rear row of seats and the bulkhead. They often stick stretchers and the like down here but it is sometimes free. Crawl into the gap and sleep on the floor. You will be turfed out by irritated cabin crew or an Air Marshall when everyone wakes up but on a few occasions, I have snatched a very satisfactory few hours sleep down there. One steward once told me it was the most cunning ploy he had ever witnessed on a long-haul flight!

UPDATE!!

This is my new "hack" for sleeping on 'planes and other forms of transport. I got one about a year ago and have tested it extensively... it's really, really useful.

ostrich light The Ostrich Pillow Light. Photo: Quora

Ostrich Pillow light — you have likely seen some of their other models but this one seems to have been less well publicised. What can I say? They are really comfortable, block out light and some sound and enable (as in the pic) you to rest your head against all sorts of otherwise uncomfortable/vibrating surfaces.