IF YOU HAVE TO SIT IN THE PASSENGER CABIN: Chat to the crews, eat everything they put in front of you, not sleep (might miss something), avoid conversation with neighbour at all costs, smoke (not any more, alas), walk around, avoid terrible in flight movie (with the sex scenes cut out), steal cutlery, think about stealing cute flight attendent, fill in landing card asap to feel efficient at immigration on arrival, listen to music (Gary Numan, Santana, Nick Drake, Harold Budd, Aries Project), stare for hours at wing and amazing landscapes beneath, meditate.
To the above list I would definitely add spotting other planes. Saw an Air 2000 757 2,000 feet below from a Virgin 747 (we were gradually overtaking, great view), stayed in formation with a Lufthansa DC10 over Nova Scotia for hours. And a Qantas 747-300 from a commuter over the mountains near Sydney.
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz