This is particularly important on steep hills, or hills with turns in the middle or at the end. Collisions with trees are not fun and are best avoided. Here are some turning tips to make your next sojourn on cross-country skis more enjoyable. If you're on the flat in untracked snow, and want to go left, simply move your left ski left, then do the same with your right ski. There's no secret to turning on the flat.
Most beginners figure out how to do it without being told.
Rather than merely pointing your skis the way you want to go and pitter-pattering around the turn, make an aggressive move to get around that turn. If going left, place your weight first on your right ski, lift your left ski slightly and point it directly to where you want to go, then shift forward onto that ski. Pushing with both poles will give you extra momentum. This is how skaters move, and it is a particularly effective way for getting around a turn. Just because you're a classic skier, that doesn't mean you can't adapt a few skating moves.