どう・いかが

どう asks how something is: 日本の生活はどうですか, "how's life in Japan?"; 昨日の映画はどうだった? "how was the film?"

いかが is its polite version, and the standard way to offer something: コーヒーはいかがですか, "would you like some coffee?"

English often says "what" where Japanese says どう: 「この服、どう思う?」 is "what do you think of these clothes?"

どうやって asks by what method: 駅までどうやって行きますか, "how do you get to the station?"

Before a noun, "what kind of" is どんな, the next point. どう itself never goes directly before a noun.