Living in ID down hill sidehilling control is a must. I had no clue until I moved over there. Out here hills where open and back then the sleds wouldn't go near the places. I moved over there and got back into sledding and immediately had to learn how to down hill side hill or pile it up in a tree. The biggest factor for me was a competitive attitude. One of my friends was learning at the same time (he was one of those guys that just does things not knowing the outcome and sometimes it works and other times it doesn't) a guy gave us some pointers and my friend went and did it like he had been doing it for a while. I was having a hard time as it feels backwards and contradictory to everything I knew. But because he did it so easy, it pis$ed me off, I took a few minutes to think and understand in my mind what needed to happen then found a little more open area and practiced, next ride I was doing it with no problems and took it to a new level. The easiest way to learn is in 3 feet of pow, almost impossible to make a mistake. For some people I will take them to a open some what steep downhill and place a snow ball or twig on the hill then have them start down the hill straight at it, then lay it over and avoid it. Same thing as laying over on the flat, turn one way and fall over, then you may or may not want to apply the throttle and the skis tips will start to dig and turn up and it will start carving sideways, usually giving it throttle brings the tail around. If you fall over and come to a stop it is very easy to start again, don't let it stand back up you are far better off keeping it all the way on its side. Another thing that gets a lot of newbies, If you are headed for a tree or what ever and your headed straight at it and you want to carve left, you have to go right first. This throws you mentally so expect it, you will go right a little and then be headed left in a hurry. Also everything downhill happens faster so think it through and make the reaction instinctively. When a hill is slick if you lay it over, sometimes it will just fall over and take off, even had the tail try to come toward me, to get it to cut and turn you have to get pressure on the rear of the tunnel and force it around while pulling on the handle bars(most likely you wont be in this position for a while), this all takes place when the sled is completely on its side. There are times I have been literally sitting on the snow sliding down the hill with both feet on one running board and the track not even touching the snow just sliding down sideways, just remember once it turns sideways keep it pulled over don't let it stand back up. If the tail starts to get farther down hill than the skis thats when you need to get it back on the track and start running the throttle. Or just stop it sideways, and then just get on it to start going again. When in doubt pin it out.
If you ever roll it make sure you stay clear of the track, I have seen these sled roll many times and when upside down the snow will pin the throttle, even seen a few guys get flung into the snow from it with injury's, Good reason to install a tether.