you could find about 400,000 posts on this with the search bar, but since it has been like a week since we had one, i'll recommend a few things.
IMHO:
-look at the end of the rail
-center your weight (use your downhill foot more) and bend your knees
-stay loose, don't force it
-commit and get a good pop onto the rail, don't just try to stick your feet to it
-i find that forcing my arms and hands down keeps me balanced better