All these really take to get going is a cold dousing of water, then a good soak. A bag provides humidity and in about three weeks, you have fresh mushrooms. When it first arrives, after initially soaking and covering it, it'll look like this:
But then, about a week later, you'll see little nubs start to grow:
And before you know it, you'll have full-fledged 'shrooms:
If your "log" dries out or stops producing... shock it with a cold water bath, and a good soak. It should recharge it and start producing delicious mushrooms once again!