When I google "dealing with jet lag", I find different advice on every web page but most only have minor differences. I avoid those web sites wanting to sell something like drugs, cosmic energy pendants, or wonder gadgets like ball caps with lights to simulate daytime.
In my experience it's about reducing travel stress and adjusting during the flight:
1) Eat regularly but lightly, just before and during flights. Besides, flying is pretty sedentary and you don't need much. Plus they generally don't provide heavy in-flight meals. They do offer coffee and this is okay, so as long it's not too close to evening hours at your destination.
2) Do not neglect your water intake, this is very important. While you cannot carry more than a few ounces of liquid on board, the attendants will have water available.
3) Helpful ideas to reduce stress during the flight are to bring something to read or bring ear buds and load some music on your phone. But be sure to disable the radio functions before turning it off for takeoff. You can then turn it back on during the flight without breaking FAA rules. In-flight TV is generally not to my taste as I don't care for the crude humor I often see. Once in a while there is a good movie or documentary. In-flight audio programming is often quite varied.
4) If they are willing, get friendly with your seat neighbor. It's a great way to pass the time and you always meet interesting individuals. But be respectful of their wishes, as they may not be interested in conversation.
5) Some people recommend shifting your sleep hours before you leave. This doesn't work for me since packing, arranging, family, and getting to the airport always seem to take all available time until the very last minute.
6) For me, in-flight sleep is never good sleep. It's sitting upright, it's noisy, it's people moving about, it's the constant vibration of engines, and it's numbing. For longer flights (more than 4-5 hours), in-flight naps are okay, but check your planned arrival time. If it is late in the day, try to stay awake. If arriving in the early morning hours, try to sleep during the flight. If you're taking a really long flight (10 hours or more), you must nap since it has the effect of making the trip seem shorter and it is your opportunity to shift your sleep hours. But think carefully about when your sleep time should be. The idea is to start sleeping during the normal hours for your destination. So, set your wrist watch for your destination shortly after takeoff. I make a habit of doing this on every leg of the trip.
7) After arriving do not try to compensate with an overly long night of sleep, 8 hours is enough. Otherwise you risk a disrupted sleep pattern for another 24 hour cycle.
8) Once you arrive, expose yourself to plenty of sunlight. While a cat nap might be okay, avoid long naps in the day time.
Hope this helps.