For a couple of days...you sound like you're doing really really well. The learning curve is short at first and then refining it takes awhile I think, but you'll never regret it once you see your fellow monoplankers walking in the flats..
Here are a few silly suggestions:
If you've got the hang of turning with your skis parallel or = (french fry turns) as oppose to snowplow turns or > (pizza/triangle turns)... then you're doing great. Next would be to start with what was suggested above...do exaggerated UP and DOWNS with your body. Bend your knees when going into turns(DOWN) and then stand taller, chest open when you're going in a straight line(UP).
UP when you're going straight and then DOWN when you're turning. Exaggerate the body and this movement at first and then you'll get to the point where the movement is very minimal . I know it sounds silly but do GROSS movements and look silly doing it and it'll lead to more FINER movements and MUSCLE memory. You'll need this as you progress for higher levels of skiing.
Next, start linking your turns with UP and DOWN movements. Start with large turns or SSSSs down a run try to use the entire width of the run and progress to smaller tighter turns all the while doing your UP(stand tall, chest open, hands in front) when going straight and DOWN(knees bent, chest closing, hands in front) when doing turns. Start from one side of the run, and then go to the other and then turn and go to the other side and then turn.CAUTION: make sure you have your peripheral vision working as to NOT get hit by others as you traverse the run.
I'm not going to get into knee positioning or feet positioning when doing your up and downs, just begin with keeping them parallel and shoulder width apart.
The next step is to try to correct your stance....which is like 95 if not 100% of the reason why your legs are SO tired. Your legs are the strongest muscle in your body and it can withstand a lot of pressure, but you need to use the quadricep part of the upper leg muscle because that's the largest part of your muscle. What you're probably doing and is sort of a good indicator if you're skiing properly is that if you find that the sides of your upper thigh or gluteus is starting to get sore....then you're sitting or leaning to far BACK in your stance. This is a common mistake in any skier. You want to be forward in your stance, bend in your knees.
One way of correcting this is to pretend like your hugging a tree and you're trying to get your arms around the trunk. Again, this sounds silly, but exaggerate this motion. You can also pretend like you're driving a truck. Anything to keep your arms forward. By doing this, it will help in improving your stance. Keep your arms forward always and your stance will gradually improve and you'll start shifting the torque in your thighs from using the side/gluteus muscle to using your center/quad muscle, and you'll last a hell of a lot longer. Once that gluteus is maxed out...it's maxed out and it's the end of your day.
Just a word of advice concerning your legs. Once you start feeling pain or soreness in your thigh...it's time to take a break if not all together stop for the day. Once it's sore, it's sore for the rest of the day. It always sounds like it's a good idea to go ONE more run, but you will become more prone to injuries. Just head straight to the bar or the hottub/ cold tub...Your day is done.
Those are some beginner tips...hopefully that helps out a little. I converted to skiing when I was tired of binding in and out on every goddamm run at our 1min/runs local hill and 3 yrs now and I've never looked back. Learn how to ski first and it'll improve your freeskiing a 1000%. Pretty soon you'll start looking less like a gayper and your stance will deviate to a freeski stance and your arms will be permanently fixed by your side and your inner thighs will burn but you won't mention it to anyone because you've center mounted your skis and it's working against the natural sidecut of the ski and then you'll be floating reverse cambered fatties down groomers all the while laughing inside at how good you look listening to MGMT...passing monowanker planks in the flatsssssssss....
