Skiing is a sport that involves physical exercise so the fitter you are the easier it will be, especially at higher altitude.
If you do not usually exercise on a regular basis, try to work on strengthening your core and leg muscles at least two months before you go skiing. Walking up and down hilly terrain is a great way to exercise both muscles and lungs.
If you are slightly older, not particularly fit and are thinking of taking lessons then we would suggest you book private lessons. This will mean that learning will be done at your pace and there is no worry about having to keep up with others.
In the resort and when skiing you will get tired, so keep yourself hydrated. You should be drinking at least a litre of water a day, if not more!