If you are travelling to a much warmer climate, bear in mind that your body will take a little time to acclimatise to the new conditions. A rapid change in temperature – especially from cold to warm – puts a sizeable strain on the circulatory system.
If you can, be in clothing that is appropriate to the climate at your destination by the time you leave the aircraft. You should also consider wearing some sort of head protection, especially in southern climes.
If you are substantially overweight or are suffering from a heart or lung condition, try to avoid any physical exertion in the first few days after you arrive.
Depending on the local humidity, you may need to make a particular point of drinking more fluids, to help your body adjust to the new climatic conditions. The rule here is: the drier the air, the more you should drink.