To go cross-country skiing near Sun Valley, Idaho, I didn't need to know a thing. Though I probably should have first verified whether there are cross-country skiing rules to follow.
For instance, I was soon having fun racing down little hills. This is where I humorously learned, on the fly, that there are no brakes (what happens if you 'round the bend and another skier is in the tracks, facing you?).
Fortunately, there are plenty of easy, meditative trails, too. The stunning beauty can't help but soothe you.