Beginner skiers tend to tense up their thighs and butts to hold up the reverse "A" shape to plow snow. If you sole rely on the leg muscles to do this, you will be able to ski only a couple of hours. Try to relax your muscles as much as you can and let the gravity do some work for you while squatting down to make the shape.
Also, try not to lean forward or backward. Beginner skiers tend to stick their butts out to balance. It is not just "pretty"
and it will get you fall down. Try to line up your head with foot.
There are more tips but they would not make much sense to you since this is your first time. Taking a lesson is strongly recommended and the instructor will tell you all things I mentioned above.
Lastly, enjoy the snow and the mountain. Geez.. after all you are going to be in Alps.