Ok heres a better way to go about it. Before you ever even try to get on a rail have one of your buddies or yourself make a decent sized line in the snow. Then practice putting the line between your legs and then poping up and turning 90 and landing on the line under your boots and keeping your weight centered. Then go and find the easiest ride on rail or box and start practicing. Just remeber to never get your weight back because that is when bad shit happens and to look down the end of the rail. And remeber don't get discouraged if you don't get it right off the bat because I know it took me and most of us 10-15 tries before it happens.
Ok mainly make sure you turn sideways, so you dont sac yourself and then second put pretty much all of your weight on your leading foot, so you dont loop out
yeaa keep your weight forward but on kinks you may have to adjust it when you hit the kink, but haunestly if you can do the basics then just keep practicing with the kinks and bigger ones