Whether you adjusted your diet, your sleep patterns or only your watch before taking off, remember that once you land, you are living in a new time frame. Even if you did not prepare your jet lag prevention strategies before the trip, it is not too late to lessen some of the effects of jet lag.
As mentioned before, keeping in mind that proteins have a stimulating effect and that carbohydrates induce relaxation and sleep can help you plan your meals to coax your biological clock. Flying east is more difficult than flying west because you tend to lose more sleep. As tired as you may be, remember to avoid taking naps so your sleep schedule at night will not be disrupted. Opt for exercise and cool showers over caffeine, and make sure your room is very dark so you can sleep at the proper time. And remember; when in Rome, eat, sleep and wake up when the Romans do!