It may be largely a matter of personal preference, but there is some evidence that flying westwards causes less jet-lag than flying eastwards. Again it is largely a matter of personal preference based on experience. Most travellers think daytime flights cause less jet-lag. The dry air in aircraft causes dehydration. Drinking plenty of non-alcoholic fluids counters this.
Water is better than coffee, tea and fruit juices.
Alcohol not only is useless in combating dehydration, but has a markedly greater intoxicating effect when drunk in the rarefied atmosphere of an airliner than it does at ground level. Sleeping aids Blindfolds, ear plugs, neckrests and blow-up pillows are all useful in helping you get quality sleep while flying. Boredom Take a book that you have meaning to read for a long time. Don't just grab any book at the airport prior to your departure. Listening to Books on Tape are is also an excellent way to pass the time - and you can have your eyes closed while you listen.