I have plenty of long haul experience and echo most of JCG's advice. Noise cancelling headphones - without something playing - are probably the biggest help to me. Not being climbed over is important but there is often concealed strip lighting along the walls so window seats are often brighter than the rest of the cabin. On a twin aisle plane you may well find that a middle seat in the centre block is darker.

I usually try to eat a good meal before boarding, with a couple of drinks, so that my napping reflex kicks in as the plane gets airborne.

Briefing the crew will not always work, I was once woken by a solicitous stewardness worried that I might starve (on an 8 hour flight!). Some airlines use stickers to warn crew what passengers wishes are, if they do, make sure that you get one.

In economy, even if you are not eating you may be asked to put your seat upright so that the passenger behind is able to. I have been woken up for this (and was not happy).

Consider booking the rearmost seat in a cabin section: the plus is that there is no one behind you so can recline without affecting others but the downside is that recline angle may be restricted.

Also, avoid toilet areas (can be another reason for avoiding last row) as people tend to gather around them, especially at the end of overnight flights.

Can't sleep on a plane? Take a day flight instead. Outbound use the time to prepare for your meeting, conference, whatever. Inbound write up your notes, follow up plan, catch up on your email, etc.