For a far destination trip, jet lag can be quite severe and something that you really would prefer to avoid. Here are few suggestions to minimize the affects of jet lag and ease the strain.
Avoid alcohol in flight, with the pressurized air in the cabin your body dehydrates substantially, and alcohol affects the body clock by not giving you a full and refreshing sleep. In fact, try to drink as much water as possible. Just ask the flying attendants for a large bottle and keep it by your seat so you can take sips whenever you want.
It is highly recommended to move around when in-flight, walk up and down the plane, do dome stretching exercises, to keep the blood circulating, and stop the joints from stiffening. While seated, swirl your ankles around from time to time.
Set your watch to the local time of your destination as you board, and sleep according to that. This helps your body to start the change in its body clock, which is so important when combating jet lag.
If you arrive at the destination by daytime, try not to go to sleep, no matter how tired you are. Instead try to go outdoors and into the sunshine if possible, this helps to alter your body clock, and will mean you will be back to normal a lot quicker.
Finally if you can't resist and your eyelids are drooping and you feel more and more tired, then set you alarm for four hours time, have a very hot bath, and then jump into bed.