どうやって

どうやって means "how" in the sense of "by what means": it asks for the method or the way to get somewhere. It goes at the front of an ordinary question, and the verb is the action you want explained.

The answer names the means with で, or gives the steps with the て-form.

どうやって or どう

どう asks what something is like, or what someone thinks of it. どうやって asks how an action is done.

• × この料理はどうやってですか → この料理はどうですか

To ask for advice rather than a method, どうしたらいいですか is the usual question.