"Wear comfortable clothing in layers. No jeans. A jacket or sweater with ample internal pockets for wallet/passport is comforting." - Andrew B (Lawyer and frequent flyer)
"Find your comfortable flying outfit, what combination of shirt, undershirt, jacket, sweater, etc. is the most comfortable to you when it's slightly colder than the room temperature. If your clothes are too warm, you will wake up needlessly. The same if you feel too cold." - Alexei Z. (Consultant and frequent flyer)
Consider Your Red Eye Time
"When flying a red-eye the sleep techniques vary by length of flight. A short red-eye such as LAX-JFK or JFK-SNN depend on the time of day. If for example you're flying from JFK to Heathrow departing at 5:00pm, you'll have significant trouble falling asleep, with many passengers first dozing off just before landing, but on that same route if you fly on the 10:00pm you have a greater chance of sleeping with your normal body cycle. " - Steven F.